急性冠脉综合征患者血浆妊娠相关蛋白A、胰岛素样生长因子Ⅰ及C反应蛋白测定的意义

目的研究急性冠状动脉综合征(ACS)患者血浆中妊娠相关蛋白A(PAPP-A),胰岛素样生长因子I(IGF-Ⅰ)及超敏C反应蛋白(hs-CRP)的变化及临床意义.方法112例经冠状动脉造影证实的冠心病患者被分为ACS组(73例),稳定型心绞痛(SAP)组(39例).20例健康人为对照组,采用酶联免疫吸附法(ELISA)检测血浆PAPP-A、IGF-Ⅰ,采用超敏免疫透视比浊法测定hs-CRP水平.结果①ACS组血浆中PAPP-A、IGF-Ⅰ和hs-CRP浓度均显著高于对照组(P＜0.01)和SAP组(P＜0.01或＜0.05);②SAP组与正常对照组之间PAPP-A、IGF-Ⅰ和hs-CRP均无显著性差异(P＞0.05);③血PAPP-A水平在ACS患者与游离的IGF-Ⅰ有明显正相关(r=0.68,P＜0.001),而与总的IGF-Ⅰ、CK-MB和cTnT无明显相关性(P＞0.05);④直线相关分析发现在ACS组hs-CRP与PAPP-A显著相关(r=0.63,P＜0.01).结论血PAPP-A、IGF-Ⅰ与hs-CRP水平在ACS患者显著升高,与动脉硬化斑块不稳定有关,可作为ACS患者的早期诊断敏感血清学标志物.     

急性冠脉综合征患者血浆妊娠相关蛋白A、C反应蛋白与内皮素测定的意义

目的:研究急性冠状动脉综合征(ACS)患者血浆妊娠相关蛋白A(PAPP-A),超敏C反应蛋白(hs-CRP)及内皮素(ET)的变化及其意义。方法:临床诊断为ACS的患者102例,被分为:急性心肌梗死(AMI)组(54例),不稳定型心绞痛(UAP)组(48例)。另选30例稳定型心绞痛(SAP)患者为SAP组和20例健康人为健康对照组,采用酶联免疫吸附法(ELISA)检测血浆PAPP-A、ET,采用超敏免疫透视比浊法测定hs-CRP水平。结果:①ACS组(AMI组和UAP组)血浆中PAPP-A[(20±6)mI U/L∶(15±4)mI U/L∶(6±4)mI U/L∶(5±5)mI U/L]、ET[(60.9±35.4)ng/L∶(52.4±33.4)ng/L∶(38.1±30.5)ng/L∶(35±19.0)ng/L]和hs-CRP[(22±11)mg/L∶(24±8)mg/L∶(3±2)mg/L∶(2±1)mg/L]浓度均显著高于SAP组和健康对照组(P0.01);②SAP组与健康对照组之间PAPP-A、ET和hs-CRP均无显著性差异(P0.05);③ACS患者血PAPP-A水平与ET及hs-CRP有明显相关(r=0.68、0.63,P均0.01),而与肌酸激酶同工酶和肌钙蛋白I无明显相关性(P均0.05)。结论:急性冠状动脉综合征患者PAPP-A、ET与hs-CRP水平显著升高,与动脉硬化斑块不稳定有关,检测其水平有助于急性冠状动脉综合征患者的早期诊断。     

基质金属蛋白酶-9和妊娠相关血浆蛋白酶A及hs-CRP与急性冠脉综合征的相关性

目的:探讨外周静脉血清基质金属蛋白酶-9(MMP-9)、妊娠相关血浆蛋白酶A(PAPP-A)、超敏C反应蛋白(hs-CRP)水平对冠状动脉粥样硬化斑块稳定性的作用。方法:选取43例急性冠脉综合征(ACS)患者为实验组,其中急性心肌梗塞(AMI)23例,不稳定型心绞痛(UAP)20例,稳定型心绞痛(SAP)25例,健康对照组13例,分别测定他们的血清MMP-9、PAPP-A、hs-CRP水平,比较各组的差异及其在ACS组中的相互关系。结果:UAP组和AMI组的MMP-9、PAPP-A和hs-CRP水平非常显著高于对照组(P<0.01),亦显著高于SAP组(P<0.05～<0.01),hs-CRP水平与MMP-9、PAPP-A水平显著相关(r=0.217,0.244,P均<0.05)。结论:MMP-9、PAPP-A、hs-CRP与斑块不稳定性密切相关,其测定有助于ACS的早期防治。     

妊娠相关血浆蛋白-A与可溶性CD40配体检测在急性冠状动脉综合征中的应用

目的探讨血浆妊娠相关血浆蛋白-A(PAPP-A)、可溶性CD40配体(sCD40L)与粥样斑块性质的关系及对急性冠状动脉综合征(ACS)危险分层的临床价值。方法随机选择稳定性心绞痛(SAP)患者42例,ACS患者76例包括急性心肌梗死(AMI)患者36例,不稳定心绞痛患者(UAP)40例和冠脉造影阴性患者38例为研究对象,电化学发光法ELISA检测血浆PAPP-A,酶联免疫吸附试验法检测血浆sCD40L,并对ACS患者进行血管内超声成像。结果血浆PAPP-A和sCD40L浓度在AMI组、UAP组和SAP组间差异显著(P<0.01),在SAP组与对照组间无差异(P>0.05),在冠脉病变单支组、双支组和三支组无差异(P>0.05),在向心性斑块和偏心性斑块之间,稳定性斑块和易损性斑块之间差异显著(P<0.01),在ACS未合并糖尿病(DM)与ACS合并DM之间差异显著(P<0.01),ACS患者血浆PAPP-A和sCD40L存在明显正相关性(r=0.862,P<0.05)。结论血浆PAPP-A和sCD40L能够反映ACS患者斑块的易损性,与ACS患者危险性密切相关,可作为临床上评价ACS患者危险程度的简单、有效、实用的方法。     

血清可溶性OX40配体和高敏C反应蛋白对冠状动脉事件的预测价值

目的观察冠心病患者血清可溶性OX40配体(sOX40L)和高敏C反应蛋白(hs-CRP)水平的变化,探讨sOX40L和hs-CRP与冠状动脉粥样斑块稳定性的关系。方法选择住院患者200例,依据不同疾病分为3组:急性冠状动脉综合征(ACS)组(90例),稳定性心绞痛(SAP)组(60例),对照组(50例)。采用透视免疫比浊法检测hs-CRP;酶联免疫吸附法检测sOX40L。所有患者均行冠状动脉造影,计算冠状动脉病变形态积分,并与sOX40L,hs-CRP水平进行相关分析。结果 ACS组sOX40L及hs-CRP水平显著高于SAP组和对照组(P<0.05),SAP组与对照组间差异无统计学意义(P>0.05);ACS组冠状动脉狭窄病变形态积分明显高于SAP组和对照组(P<0.05),SAP组与对照组间病变积分差异无统计学意义(P>0.05);ACS患者sOX40L和hs-CRP水平与冠状动脉造影狭窄病变形态积分有明显相关性(P<0.05);sOX40L与hs-CRP呈显著正相关(r=0.48,P<0.01)。结论冠心病患者血清sOX40L、hs-CRP水平升高可能提示斑块不稳定;血清sOX40L、hs-CRP水平可以有效判断冠状动脉病变程度,预测急性冠状动脉事件的发生。     

妊娠相关性血浆蛋白-A在急性冠脉综合征患者中的临床意义

目的通过检测不同冠心病组及对照组外周血妊娠相关性血浆蛋白-A(PAPP-A)水平,以明确其与冠脉综合征(AS)不稳定斑块的相关关系,探讨PAPP-A在急性冠脉综合征(ACS)中的可能机制。方法使用酶联免疫吸附法(ELISA)分别测定40例急性心肌梗死(AMI)、37例不稳定型心绞痛(UAP)、38例稳定型心绞痛(SAP)及33名非冠心病对照组血中PAPP-A、游离的及总的IGF-I水平。结果血PAPP-A水平在ACS患者明显高于SAP及对照组(P<0.01);与游离的IGF-I存在明显的正相关(P<0.01),而与CK-MB、cTnI无明显相关性(P>0.05)。结论血PAPP-A水平升高与AS斑块的不稳定性有关,提示可作为识别ACS的早期血清学标志物,且其水平的升高与心肌坏死无关。     

ACS患者血浆MMP-9及hs-CRP水平与冠状动脉病变的相关性

目的:探讨急性冠状动脉综合征(ACS)患者外周血浆基质金属蛋白酶-9(MMP-9)、超敏C反应蛋白(hs-CRP)水平与冠脉病变的相关性。方法:选择ACS患者60例,其中急性心肌梗死(AMI)30例(AMI组),不稳定型心绞痛(UAP)30例(UAP组);另选同期住院的稳定型心绞痛(SAP)30例(SAP组)及非冠心病患者30例(对照组);采用酶联免疫吸附(ELISA)法分别测定各组患者外周血浆MMP-9及hs-CRP水平,并与冠状动脉造影Gensini积分行相关性分析。结果:各组血浆MMP-9与hs-CRP水平均差异有统计学意义,其中AMI组>UAP组>SAP组>对照组(均P<0.05);与对照组比较,AMI组、UAP组及SAP组Gensini评分均增大(均P<0.05);血浆MMP-9水平与hs-CRP水平呈显著正相关性(r=0.881,P<0.05),血浆MMP-9水平与Gensini评分之间无相关性(r=0.392,P>0.05)。结论:急性ACS患者血浆MMP-9和hs-CRP水平可以预测冠状动脉病变的稳定性,但不能预测病变程度。     

冠心病患者血清脂联素和高敏C反应蛋白的观察

目的探讨冠心病患者血清脂联素和高敏C反应蛋白(hs-CRP)水平的相关性。方法可疑冠心病患者83例行冠状动脉造影,确诊冠心病患者65例,分为稳定性心绞痛组(SAP组,21例)和急性冠状动脉综合征组(ACS组,44例),冠状动脉造影正常者作为对照组(18例)。测定各组患者血清脂联素和hs-CRP水平。结果ACS组患者血清脂联素对数水平较对照组和SAP组明显降低(P<0.05);ACS组患者hs-CRP水平高于SAP组和对照组(P<0.05)。线性相关分析表明,血清脂联素对数与hs-CRP水平呈负相关(r=-0.25,P<0.05)。结论血清脂联素与hs-CRP相互作用可能共同参与了冠状动脉粥样硬化的发生与发展。     

急性冠状动脉综合征妊娠相关血浆蛋白-A与C反应蛋白和肿瘤坏死因子-α相关性的研究

目的:研究急性冠状动脉综合征(ACS)患者妊娠相关血浆蛋白A(PAPP-A)血清水平和外周血单核细胞表达的变化及其与C反应蛋白(CRP)和肿瘤坏死因子-α(TNF-α)的相关性。方法:测定18例不稳定型心绞痛(UAP组)、37例急性心肌梗死(AMI组)和15例稳定型心绞痛(SAP组)及15例正常对照者(对照组)的血清PAPP-A、高敏CRP(hsCRP)和TNF-α水平。同时分离外周血单核细胞,应用RT-PCR检测PAPP-A和TNF-α的mRNA表达。结果:SAP组血清hsCRP和TNF-α水平明显高于对照组;UAP组明显高于对照组和SAP组,但低于AMI组。SAP组血清PAPP-A水平和单核细胞PAPP-A的mRNA表达水平与对照组相比,差异无统计学意义;而在UAP组和AMI组均显著高于对照组和SAP组(均P<0.01)。ACS组患者的血清PAPP-A水平与血清hsCRP和TNF-α水平均呈显著正相关(r=0.616,r=0.712,P<0.01),同时外周血单核细胞PAPP-AmR-NA表达水平与血清hsCRP水平及TNF-αmRNA表达水平均呈显著正相关(r=0.706,r=0.733,P<0.01)。结论:PAPP-A可能是由活化的单核细胞合成并分泌到动脉粥样硬化斑块内和血循环中,并与炎症密切相关。     

冠心病患者高敏C反应蛋白、基质金属蛋白酶-9及妊娠相关血浆蛋白A水平及临床意义

目的 探讨不同类型冠心病患者外周静脉及冠状动脉血高敏C反应蛋白（hs-CRP）、基质金属蛋白酶-9（MMP-9）和妊娠相关血浆蛋白A（PAPP-A）水平及及临床意义.方法 连续入选150例冠心病（CHD）患者,其中急性心肌梗死组（AMI组）40例、不稳定型心绞痛组（UAP组）60例、稳定型心绞痛组（SAP组）50例,另外选择冠状动脉造影正常的受试者20例作为对照组.分别检测受试者外周静脉及冠状动脉血hs-CRP、MMP-9及PAPP-A水平,进行组间及不同外周静脉及冠状动脉血间指标差异比较.结果 UAP组、AMI组外周静脉血及冠状动脉血hs-CRP、MMP-9和PAPP-A水平显著增高,与对照组及SAP组比较,均有明显统计学差异（P＜0.05～0.01）;AMI组与UAP组比较,血hs-CRP、MMP-9和PAPP-A水平亦有显著统计学差异（P＜0.01）;但SAP组与对照组比较,血hs-CRP、MMP-9和PAPP-A水平无统计学差异（P＞0.05）.外周静脉血及冠状动脉血hs-CRP、MMP-9、PAPP-A相互间呈显著正相关性（P均＜0.05）.结论 hs-CRP、MMP-9及PAPP-A与急性冠脉综合征（ACS）发病密切相关,其测定有助于ACS的早期诊治.     

A thermodynamic definition of protein domains

Protein domains are conspicuous structural units in globular proteins, and their identification has been a topic of intense biochemical interest dating back to the earliest crystal structures. Numerous disparate domain identification algorithms have been proposed, all involving some combination of visual intuition and/or structure-based decomposition. Instead, we present a rigorous, thermodynamically-based approach that redefines domains as cooperative chain segments. In greater detail, most small proteins fold with high cooperativity, meaning that the equilibrium population is dominated by completely folded and completely unfolded molecules, with a negligible subpopulation of partially folded intermediates. Here, we redefine structural domains in thermodynamic terms as cooperative folding units, based on m-values, which measure the cooperativity of a protein or its substructures. In our analysis, a domain is equated to a contiguous segment of the folded protein whose m-value is largely unaffected when that segment is excised from its parent structure. Defined in this way, a domain is a self-contained cooperative unit; i.e., its cooperativity depends primarily upon intrasegment interactions, not intersegment interactions. Implementing this concept computationally, the domains in a large representative set of proteins were identified; all exhibit consistency with experimental findings. Specifically, our domain divisions correspond to the experimentally determined equilibrium folding intermediates in a set of nine proteins. The approach was also proofed against a representative set of 71 additional proteins, again with confirmatory results. Our reframed interpretation of a protein domain transforms an indeterminate structural phenomenon into a quantifiable molecular property grounded in solution thermodynamics.     

Fibrillation precursor of superoxide dismutase 1 revealed by gradual tuning of the protein-folding equilibrium

Although superoxide dismutase 1 (SOD1) stands out as a relatively soluble protein in vitro, it can be made to fibrillate by mechanical agitation. The mechanism of this fibrillation process is yet poorly understood, but attains considerable interest due to SOD1’s involvement in the neurodegenerative disease amyotrophic lateral sclerosis (ALS). In this study, we map out the apoSOD1 fibrillation process from how it competes with the global folding events at increasing concentrations of urea: We determine how the fibrillation lag time (τ_lag) and maximum growth rate (ν_max) depend on gradual titration of the folding equilibrium, from the native to the unfolded state. The results show that the agitation-induced fibrillation of apoSOD1 uses globally unfolded precursors and relies on fragmentation-assisted growth. Mutational screening and fibrillation m-values (∂ log τ_lag/∂[urea] and ∂ log ν_max/∂[urea]) indicate moreover that the fibrillation pathway proceeds via a diffusely bound transient complex that responds to the global physiochemical properties of the SOD1 sequence. Fibrillation of apoSOD1, as it bifurcates from the denatured ensemble, seems thus mechanistically analogous to that of disordered peptides, save the competing folding transition to the native state. Finally, we examine by comparison with in vivo data to what extent this mode of fibrillation, originating from selective amplification of mechanically brittle aggregates by sample agitation, captures the mechanism of pathological SOD1 aggregation in ALS.     

In vivo protein stabilization based on fragment complementation and a split GFP system

Protein stabilization was achieved through in vivo screening based on the thermodynamic linkage between protein folding and fragment complementation. The split GFP system was found suitable to derive protein variants with enhanced stability due to the correlation between effects of mutations on the stability of the intact chain and the effects of the same mutations on the affinity between fragments of the chain. PGB1 mutants with higher affinity between fragments 1 to 40 and 41 to 56 were obtained by in vivo screening of a library of the 1 to 40 fragments against wild-type 41 to 56 fragments. Colonies were ranked based on the intensity of green fluorescence emerging from assembly and folding of the fused GFP fragments. The DNA from the brightest fluorescent colonies was sequenced, and intact mutant PGB1s corresponding to the top three sequences were expressed, purified, and analyzed for stability toward thermal denaturation. The protein sequence derived from the top fluorescent colony was found to yield a 12 °C increase in the thermal denaturation midpoint and a free energy of stabilization of -8.7 kJ/mol at 25 °C. The stability rank order of the three mutant proteins follows the fluorescence rank order in the split GFP system. The variants are stabilized through increased hydrophobic effect, which raises the free energy of the unfolded more than the folded state; as well as substitutions, which lower the free energy of the folded more than the unfolded state; optimized van der Waals interactions; helix stabilization; improved hydrogen bonding network; and reduced electrostatic repulsion in the folded state.     

Experimental support for the evolution of symmetric protein architecture from a simple peptide motif

The majority of protein architectures exhibit elements of structural symmetry, and "gene duplication and fusion" is the evolutionary mechanism generally hypothesized to be responsible for their emergence from simple peptide motifs. Despite the central importance of the gene duplication and fusion hypothesis, experimental support for a plausible evolutionary pathway for a specific protein architecture has yet to be effectively demonstrated. To address this question, a unique "top-down symmetric deconstruction" strategy was utilized to successfully identify a simple peptide motif capable of recapitulating, via gene duplication and fusion processes, a symmetric protein architecture (the threefold symmetric β-trefoil fold). The folding properties of intermediary forms in this deconstruction agree precisely with a previously proposed "conserved architecture" model for symmetric protein evolution. Furthermore, a route through foldable sequence-space between the simple peptide motif and extant protein fold is demonstrated. These results provide compelling experimental support for a plausible evolutionary pathway of symmetric protein architecture via gene duplication and fusion processes.     

Membrane protein thermodynamic stability may serve as the energy sink for sorting in the periplasm

Thermodynamic stabilities are pivotal for understanding structure–function relationships of proteins, and yet such determinations are rare for membrane proteins. Moreover, the few measurements that are available have been conducted under very different experimental conditions, which compromises a straightforward extraction of physical principles underlying stability differences. Here, we have overcome this obstacle and provided structure–stability comparisons for multiple membrane proteins. This was enabled by measurements of the free energies of folding and the m values for the transmembrane proteins PhoP/PhoQ-activated gene product (PagP) and outer membrane protein W (OmpW) from Escherichia coli. Our data were collected in the same lipid bilayer and buffer system we previously used to determine those parameters for E. coli outer membrane phospholipase A (OmpLA). Biophysically, our results suggest that the stabilities of these proteins are strongly correlated to the water-to-bilayer transfer free energy of the lipid-facing residues in their transmembrane regions. We further discovered that the sensitivities of these membrane proteins to chemical denaturation, as judged by their m values, was consistent with that previously observed for water-soluble proteins having comparable differences in solvent exposure between their folded and unfolded states. From a biological perspective, our findings suggest that the folding free energies for these membrane proteins may be the thermodynamic sink that establishes an energy gradient across the periplasm, thus driving their sorting by chaperones to the outer membranes in living bacteria. Binding free energies of these outer membrane proteins with periplasmic chaperones support this energy sink hypothesis.     

Folding without charges

Surface charges of proteins have in several cases been found to function as “structural gatekeepers,” which avoid unwanted interactions by negative design, for example, in the control of protein aggregation and binding. The question is then if side-chain charges, due to their desolvation penalties, play a corresponding role in protein folding by avoiding competing, misfolded traps? To find out, we removed all 32 side-chain charges from the 101-residue protein S6 from Thermus thermophilus. The results show that the charge-depleted S6 variant not only retains its native structure and cooperative folding transition, but folds also faster than the wild-type protein. In addition, charge removal unleashes pronounced aggregation on longer timescales. S6 provides thus an example where the bias toward native contacts of a naturally evolved protein sequence is independent of charges, and point at a fundamental difference in the codes for folding and intermolecular interaction: specificity in folding is governed primarily by hydrophobic packing and hydrogen bonding, whereas solubility and binding relies critically on the interplay of side-chain charges.     

Functional modulation of a protein folding landscape via side-chain distortion

Ultrahigh-resolution (< 1.0 Å) structures have revealed unprecedented and unexpected details of molecular geometry, such as the deformation of aromatic rings from planarity. However, the functional utility of such energetically costly strain is unknown. The 0.83 Å structure of α-lytic protease (αLP) indicated that residues surrounding a conserved Phe side-chain dictate a rotamer which results in a ∼6° distortion along the side-chain, estimated to cost 4 kcal/mol. By contrast, in the closely related protease Streptomyces griseus Protease B (SGPB), the equivalent Phe adopts a different rotamer and is undistorted. Here, we report that the αLP Phe side-chain distortion is both functional and conserved in proteases with large pro regions. Sequence analysis of the αLP serine protease family reveals a bifurcation separating those sequences expected to induce distortion and those that would not, which correlates with the extent of kinetic stability. Structural and folding kinetics analyses of family members suggest that distortion of this side-chain plays a role in increasing kinetic stability within the αLP family members that use a large Pro region. Additionally, structural and kinetic folding studies of mutants demonstrate that strain alters the folding free energy landscape by destabilizing the transition state (TS) relative to the native state (N). Although side-chain distortion comes at a cost of foldability, it suppresses the rate of unfolding, thereby enhancing kinetic stability and increasing protein longevity under harsh extracellular conditions. This ability of a structural distortion to enhance function is unlikely to be unique to αLP family members and may be relevant in other proteins exhibiting side-chain distortions.     

Retro-translocation of mitochondrial intermembrane space proteins

The content of mitochondrial proteome is maintained through two highly dynamic processes, the influx of newly synthesized proteins from the cytosol and the protein degradation. Mitochondrial proteins are targeted to the intermembrane space by the mitochondrial intermembrane space assembly pathway that couples their import and oxidative folding. The folding trap was proposed to be a driving mechanism for the mitochondrial accumulation of these proteins. Whether the reverse movement of unfolded proteins to the cytosol occurs across the intact outer membrane is unknown. We found that reduced, conformationally destabilized proteins are released from mitochondria in a size-limited manner. We identified the general import pore protein Tom40 as an escape gate. We propose that the mitochondrial proteome is not only regulated by the import and degradation of proteins but also by their retro-translocation to the external cytosolic location. Thus, protein release is a mechanism that contributes to the mitochondrial proteome surveillance.Mitochondrial biogenesis is essential for eukaryotic cells. Because most mitochondrial proteins originate in the cytosol, mitochondria had to develop a protein import system. Given the complex architecture of these organelles, with two membranes and two aqueous compartments, protein import and sorting require the cooperation of several pathways. The main entry gate for precursor proteins is the translocase of the outer mitochondrial membrane (TOM) complex. Upon entering mitochondria, proteins are routed to different sorting machineries (1–5).Reaching the final location is one step in the maturation of mitochondrial proteins that must be accompanied by their proper folding. The mitochondrial intermembrane space assembly (MIA) pathway for intermembrane space (IMS) proteins illustrates the importance of coupling these processes because this pathway links protein import with oxidative folding (6–10). Upon protein synthesis in the cytosol, the cysteine residues of IMS proteins remain in a reduced state, owing to the reducing properties of the cytosolic environment (11, 12). After entering the TOM channel, precursor proteins are specifically recognized by Mia40 protein, and their cysteine residues are oxidized through the cooperative action of Mia40 and Erv1 proteins (7, 13–17). Mia40 is a receptor, folding catalyst, and disulfide carrier, and the Erv1 protein serves as a sulfhydryl oxidase. The oxidative folding is believed to provide a trapping mechanism that prevents the escape of proteins from the IMS back to the cytosol (10, 13, 18). Our initial result raised a possibility that the reverse process can also occur, as we observed the relocation of in vitro imported Tim8 from mitochondria to the incubation buffer (13). Thus, we sought to establish whether and how this process can proceed in the presence of the intact outer membrane (OM). Our study provides, to our knowledge, the first characterization of the mitochondrial protein retro-translocation. The protein retro-translocation serves as a regulatory and quality control mechanism for the mitochondrial IMS proteome.     

Pancreatic stone protein – sepsis and the riddles of the exocrine pancreas

Pancreatic stone protein (PSP), discovered in the 1970ies, was first associated with stone formation during chronic pancreatitis. Later, the same protein was independently detected in islet preparations and named regenerating protein 1 (REG1). Additional isoforms of PSP, including pancreatitis-associated protein (PAP), belong to the same protein family. Although the names indicate a potential function in stone formation or islet regeneration, involvements in cellular processes were only suggestive and never unequivocally proven. We established an association between PSP levels in patient blood samples and the development of sepsis. In this review, written in connection with receiving the Lifetime Achievement Award of the European Pancreatic Club, the evolution of the sepsis aspect of PSP is described. We conclude that the true functional properties of this fascinating pancreatic protein still remain an enigma.     

Computing protein stabilities from their chain lengths

New amino acid sequences of proteins are being learned at a rapid rate, thanks to modern genomics. The native structures and functions of those proteins can often be inferred using bioinformatics methods. We show here that it is also possible to infer the stabilities and thermal folding properties of proteins, given only simple genomics information: the chain length and the numbers of charged side chains. In particular, our model predicts ΔH(T), ΔS(T), ΔC_p, and ΔF(T) —the folding enthalpy, entropy, heat capacity, and free energy—as functions of temperature T; the denaturant m values in guanidine and urea; the pH-temperature-salt phase diagrams, and the energy of confinement F(s) of the protein inside a cavity of radius s. All combinations of these phase equilibria can also then be computed from that information. As one illustration, we compute the pH and salt conditions that would denature a protein inside a small confined cavity. Because the model is analytical, it is computationally efficient enough that it could be used to automatically annotate whole proteomes with protein stability information.