人类白细胞抗原(HLA)系统:1990

人类白细胞抗原(HLA)是细胞表面蛋白质,可分为Ⅰ类和Ⅱ类,它们在结构、功能和组织分布方面不同,由一系列紧密联锁的多态基因控制,总称为组织相容性复合体(MHC)。 HLA的结构和多态性 MHC基因位于第六对染色体的短臂上,末端以Ⅰ类位点臂内延伸为Ⅱ类位点。近来,用X线结晶学确定了Ⅰ类分子的结构,发现存在于细胞表面的蛋白质复合物是由二对结构相似的区域构成。α_3区域及其连接的β_2-微球蛋白表明免疫球蛋白恒定区的相似性,这些区域可能影响HLA复合物的特异性,强度和稳定性。α_3区是T细胞上辅助蛋白CD8的结合位点,是Ⅰ类抗原有效限制T细胞活化所必需的。α_1、α_2区在C-末端被2个α螺旋联在一起,形成一单个的β折叠结构。在两个螺旋之间,是假设的抗原结合位点。对α_3区和α_1区位点间作比较,无明显差别。然而α_1区在α螺旋中是多变的,在β折叠中有稳定的成份,提示这可能为肽的结合提供支架,在β折叠中α_2区是多变的,并且可能与T细胞受体(TCR)的相互作用有关,以及在肽的选择中起作用。Ⅱ类或HLA-D区蛋白质由DR、DQ和DP位点编码。它由一个33kd的A链和一个29kd的B链     

转化生长因子-β1(TGF-β1)与肺纤维化研究的进展

转化生长因子-β1（Transformating Growth Factorbetal，TGF-β1）是一种多功能的细胞因子，是由2条分子量为11Kd有112个氨基酸构成的单链通过二硫键结合而成的分子量为25Kd的多肽。它在细胞的生长、分化、免疫调节、调节细胞外基质（Extracellular matrix，ECM）合成及损伤后的修复方面发挥着重要的作用。在哺乳动物中。TGF—β家族有3个亚型TGF—β1、TGF-β2、TGF—β3，它们通过与相应的受体结合而发挥生物作用。活化的TGF—β过度表达对肺、     

人类GM-CSF受体胞外结构域及功能的研究进展

人类粒-巨噬细胞集落刺激因子(granulocyte-macrophage colony-stimulating factor,GM-CSF)通过细胞膜表面特异性受体(GM-CSF receptor,GMR)介导维持细胞存活,刺激细胞增殖与分化,调节成熟细胞功能。GMR为跨膜受体由α链和β链共同组成,结构上分为胞外域、跨膜部分和胞内域。α链和β链胞外域均含有一种造血生长因子受体超家族的共同结构模体(cytokine receptor modules,CRM)并依靠保守的半胱氨酸残基形成的二硫键维持胞外空间结构。GM-CSF和α链通过电荷识别结合并诱导β链加入,形成完整的配体受体复合物。在二硫键的作用下,GMR多聚化使两条以上β链胞内部分相互接近活化JAK2,完成GM-CSF对细胞的激活过程。     

白细胞介素-22(IL-22)及其研究现状

白细胞介素22（IL-22）是2000年由Dumoutier等发现的-种新型细胞因子，与IL-10有23％的同源性，曾被命名为IL-TIF（Interleukin-10-related T cell—derived inducible factor）。鉴于与IL-10的结构相似，其受体是-个Ⅱ型细胞因子受体家族的新成员，以及其在白细胞内的产物和作用的确认，由Xie等将它重命名为人类细胞因子白细胞介素-22（Interleukin-22，IL-22）。目前对它的研究尚处于起始阶段。     

载脂蛋白M的生物学特性及其研究进展

载脂蛋白是脂蛋白的组成成分,生理功能是构成并稳定脂蛋白的结构,参与脂蛋白与细胞表面脂蛋白受体的结合及其代谢过程。迄今发现的载脂蛋白已有20余种,它们通过不同的途径调节体内的脂质代谢。载脂蛋白M（apolipoprotein M,apo M）是新近发现的一种载脂蛋白,是疏水性分子结合蛋白家族（1ipocalin family）成员。apo M基因存在于所有哺乳动物中,且具有极高的同源性。目前apoM在机体内的合成及表达的生理意义尚不明确,我们就apo M的生物学特性和其在相关领域的研究进展作一综述。     

趋化性细胞因子与器官炎症损伤关系研究进展

趋化性细胞因子(ch-K)是体内有趋化细胞作用的多肽类物质,其作用机制是通过特殊的信号传递系统,激活白细胞表面的粘附分子(CAM),后者与血管内皮细胞的相互作用促使白细胞游向炎症区域,使白细胞、吞噬细胞、单核细胞脱颗粒并释放某些酶产物发挥其效应。现对Ch-K的结构,生物性特点综述如下。1　ch-K种类及趋化细胞作用ch-K结构特点是由4个保守的半胱氨酸碱基(CYs)形成2个分子连接的双硫键桥。根据2个近端的最大的CYs排列顺序不同分为α(C-X-C)亚家族,即在CYs间插有一个氨基酸分子,以X代表;和β(C-C)亚家族,是指CYs呈直接联接方式。ch…     

IL-12家族抗肿瘤作用的研究进展

IL-12家族是一类结构相似、共价结合的异二聚体细胞因子家族,目前其主要成员包括 IL-12、IL-23、IL-27和 IL-35。IL-12由 p35和 p40两个亚基通过二硫键结合形成,是细胞免疫应答过程中的关键调节因子,在激活 NK 细胞、T 细胞,并诱使其分泌大量 IFN-γ,抑制肿瘤血管生成等方面具有重要的作用。IL-23由 p40和 p19亚基以二硫键结合形成,在抗肿瘤及抗自身免疫病中发挥着重要作用。IL-27由 p28和 EBI3亚基通过二硫键结合形成,在维持机体免疫系统的自身稳定、抗感染及抗肿瘤中起着重要的作用。IL-35由 p35和 EBI3亚基通过二硫键结合形成,在抑制效应 T 细胞增殖、Th17细胞分化和 IL-17的合成方面发挥重要作用。随着 IL-12家族成员的丰富,IL-12家族成员的功能研究也越来越深入,近年来大量研究认为 IL-12家族在肿瘤的发生、发展中具有至关重要的作用,因此,本文就 IL-12家族与其抗肿瘤作用的研究作一综述。     

趋化素样因子1研究进展

趋化因子家族是一类由免疫或非免疫细胞分泌的一级结构相似的小分子蛋白,在机体的免疫调节、过敏反应、炎症反应、细胞增殖分化等过程中发挥重要作用。趋化因子超家族成员具有一定的同源结构,根据一级结构中保守的4～6个Cys的前2个Cys的排列方式,可将趋化因子超家族分为CXC（α）、CC（β）、C（γ）和CX3C（）四个亚家族,它们的功能除趋化活性外,还具有细胞活化等多种生物学效应。这些趋化因子与七次跨膜的G蛋白偶联受体特异结合,通过G蛋白转导信号至细胞内,发挥其生物学活性。目前已发现28种CCL、16种CX—CL、2种CL和1种CX3CL。     

载脂蛋白M的生物学特性及其研究进展

载脂蛋白是脂蛋白的组成成分,生理功能是构成并稳定脂蛋白的结构,参与脂蛋白与细胞表面脂蛋白受体的结合及其代谢过程。迄今发现的载脂蛋白已有20余种,它们通过不同的途径调节体内的脂质代谢。载脂蛋白M(apolipoprotein M,apo M)是新近发现的一种载脂蛋白,是疏水性分子结合蛋白     

血S1OOB蛋白水平检测在临床应用的研究进展

1965年,Moore等[1,2]首先在牛脑组织中发现S100蛋白,因该蛋白在中性饱和硫酸铵中100%溶解而得名.它是一种分子量较小(13～21 DK)的EF手型(螺旋-环-螺旋)钙结合蛋白,由A和B两个亚单位组成的二聚体[1-3].S100蛋白家族目前已经发现有20个成员,其中S100 A1和S100B是主要成分,前者由一个α链和一个β链构成,后者由两个β链构成[2].     

Prediction of the key binding site of odorant‐binding protein of Holotrichia oblita Faldermann (Coleoptera: Scarabaeida)

The scarab beetle Holotrichia oblita Faldermann (Coleoptera: Scarabaeidae) is a predominant underground pest in the northern parts of China, and its larvae (grubs) cause great economic losses because of its wide range of host plants and covert habitats. Environmentally friendly strategies for controlling adults would have novel and broad potential applications. One potential pest management measure is the regulation of olfactory chemoreception to control target insect pests. In the process of olfactory recognition, odorant‐binding proteins (OBPs) are believed to carry hydrophobic odorants from the environment to the surface of olfactory receptor neurons. To obtain a better understanding of the relationship between OBP structures and their ligands, homology modelling and molecular docking have been conducted on the interaction between HoblOBP1 and hexyl benzoate in the present study. Based on the results, site‐directed mutagenesis and binding experiments were combined to describe the binding sites of HoblOBP1 and to explore its ligand‐binding mechanism. After homology modelling of HoblOBP1, it was found that the three‐dimensional structure of HoblOBP1 consists of six α‐helices and three disulphide bridges that connect the helices, and the hydrophobic pockets are both composed of five helices. Based on the docking study, we found that van der Waals interactions and hydrophobic interactions are both important in the bonding between HoblOBP1 and hexyl benzoate. Intramolecular residues formed the hydrogen bonds in the C terminus of the protein and the bonds are crucial for the ligand‐binding specificity. Finally, MET48, ILE80 and TYR111 are binding sites predicted for HoblOBP1. Using site‐directed mutagenesis and fluorescence assays, it was found that ligands could not be recognized by mutant of Tyr111. A possible explanation is that the compound could not be recognized by the mutant, and remains in the binding cavity because of the loss of the intramolecular hydrogen bonding that acts as a holder. So we believe that Tyr111 of HoblOBP1 is a key binding site. We also believe that Ile80A is a very important binding site, especially to some ligands.     

Chemical structure, active sites and receptor binding of insulin molecule and its signal transduction]

Biologically active insulin consists of two polypeptide chains, the A chain(21 amino acids) and the B chain(30 amino acids). Several regions of invariability closely related to the biological activity, such as (a) the position of cysteines that form the disulfide bridges, (b) the N- and C-terminal regions of the A-chain, and (c) hydrophobic residues at the C-terminus of the B chain. The functional insulin receptor is a heterotetrameric protein composed of two alpha and two beta subunits. The alpha subunits contain the insulin binding site and the binding causes conformational changes in the receptor molecule. The quaternary structure of the beta subunit then changes to allow for stimulating autophosphorylation of its tyrosine residues. Those in the catalytic domain(tyrosines 1146, 1150, 1151) are essential to promote the kinase activity of the receptor toward other protein substrates in insulin signalling system. The elucidation of detailed mechanisms of insulin binding to the receptor will be useful for the development of a novel hypoglycemic agent 'insulin receptor agonist', which directly acts on the insulin site and can be orally administered for the treatment of diabetes mellitus.     

Coupling of receptors to G proteins, pharmacological implications.

There are four main classes of membrane-bound receptors: receptors which are also enzymes (tyrosine protein-kinase or guanylate cyclase), receptor channels, receptors coupled to G proteins (GTP binding proteins) and receptors with unknown transduction mechanisms. Receptors coupled to G proteins which have been cloned, constitute a superfamily of proteins containing seven hydrophobic transmembrane helices. The binding site of the ligand is within the hydrophobic core of the protein and the domain of interaction of the G proteins is constituted by the N- and C-terminal parts of the third intracellular loop, plus the C-terminal tail, adjacent to the transmembrane VII. G proteins themselves are also members of another superfamily. These proteins have highly conserved domains constituting the GTP binding site and they interact with the receptors by their C-terminal parts. Compounds such as mastoparan, substance P and 48/80 directly stimulate G proteins, an action which probably mediates their exocytotic properties. A high degree of homologies between G protein-linked receptors explains the non-specificity of some antagonists (like beta-adrenergic blocking agents on 5-HT1 receptors). The discovery of new members of the G protein-linked receptors which have not yet been pharmacologically characterized, raises the problem of receptor classification.     

The human immunodeficiency virus gp120 binding site on CD4: delineation by quantitative equilibrium and kinetic binding studies of mutants in conjunction with a high-resolution CD4 atomic structure

The first immunoglobulin V-like domain of CD4 contains the binding site for human immunodeficiency virus gp120. Guided by the atomic structure of a two-domain CD4 fragment, we have examined gp120 interaction with informative CD4 mutants, both by equilibrium and kinetic analysis. The binding site on CD4 appears to be a surface region of about 900 A2 on the C" edge of the domain. It contains an exposed hydrophobic residue, Phe43, on the C" strand and four positively charged residues, Lys29, Lys35, Lys46, and Arg59, on the C, C', C", and D strands, respectively. Replacement of Phe43 with Ala or Ile reduces affinity for gp120 by more than 500-fold; Tyr, Trp, and Leu substitutions have smaller effects. The four positively charged side chains each make significant contributions (7-50-fold). This CD4 site may dock into a conserved hydrophobic pocket bordered by several negatively charged residues in gp120. Class II major histocompatibility complex binding includes the same region on CD4; this overlap needs to be considered in the design of inhibitors of the CD4-gp120 interaction.     

Determinants of ligand selectivity at the kappa-receptor based on the structure of the orphanin FQ receptor

It is unclear how opioid selectivity and activation are regulated within the receptor core. In previous studies, the OFQ receptor was converted into a functional opioid receptor by mutating five amino acids at three sites to the corresponding residues conserved across the mu-, kappa-, and delta-opioid receptors, suggesting that these sites comprise an opioid binding pocket. To examine this hypothesis, the present study examines whether these conserved residues represent an opioid binding pocket in the context of the opioid receptors, i.e., does their removal from opioid receptors destroy opioid ligand binding? The reciprocal mutations K227A (transmembrane [TM]5), IHI290-292VQV (TM6), and I316T (TM7) were evaluated in the kappa-opioid receptor. In terms of alkaloid binding, there were no changes in affinity for mutants K227A and IHI290-292VQV. At mutant I316T, antagonist binding was unaltered, but there was a trend toward slightly decreased agonist affinity. In contrast, the binding of peptides had a more complex pattern. Again, K227A and IHI290-292VQV did not decrease the binding affinity of dynorphin-related peptides. Mutant I316T had 10- to 20-fold decreased affinity for dynorphin-related peptides, suggesting that I316 is part of a critical dynorphin recognition site. In response to alkaloid stimulation, I316T activated more G-protein(s) than wild type, and similar levels were observed in response to dynorphin stimulation. Overall, these results suggest that ligands are capable of achieving high-affinity binding through interaction with multiple sites/conformations of the receptor. These different modes of interaction have different down-stream results in terms of receptor activation and signal transduction.     

The binding affinity of human IgG for its high affinity Fc receptor is determined by multiple amino acids in the CH2 domain and is modulated by the hinge region.

A family of chimeric immunoglobulins (Igs) bearing the murine variable region directed against the hapten dansyl linked to human IgG1, -2, -3, and -4 has been characterized with respect to binding to the human high affinity Fc gamma receptor, Fc gamma RI. Chimeric IgG1 and -3 have the highest affinity association (Ka = 10(9) M-1), IgG4 is 10-fold reduced from this level, and IgG2 displays no detectable binding. A series of genetic manipulations was undertaken in which domains from the strongly binding subclass IgG3 were exchanged with domains from the nonbinding subclass IgG2. The subclass of the CH2 domain was found to be critical for determining IgG receptor affinity. In addition, the hinge region was found to modulate the affinity of the IgG for Fc gamma RI, possibly by determining accessibility of Fc gamma RI to the binding site on Fc. A series of amino acid substitutions were engineered into the CH2 domain of IgG3 and IgG4 at sites considered potentially important to Fc receptor binding based on homology comparisons of binding and nonbinding IgG subclasses. Characterization of these mutants has revealed the importance for Fc gamma RI association of two regions of the genetic CH2 domain separated in primary structure by nearly 100 residues. The first of these is the hinge-link or lower hinge regions, in which two residues, Leu (234) and Leu(235) in IgG1 and -3, are critical to high affinity binding. Substitution at either of these sites reduces the IgG association constant by 10-100-fold. The second region that appears to contribute to receptor binding is in a hinge-proximal bend between two beta strands within the CH2 domain, specifically, Pro(331) in IgG1 and -3. As a result of beta sheet formation within this domain, this residue lies within 11 A of the hinge-link region. Substitution at this site reduces the Fc receptor association constant by 10-fold.     

Identification of the principal proteoglycan-binding site in LDL. A single-point mutation in apo-B100 severely affects proteoglycan interaction without affecting LDL receptor binding.

The subendothelial retention of LDLs through their interaction with proteoglycans has been proposed to be a key process in the pathogenesis of atherosclerosis. In vitro studies have identified eight clusters of basic amino acids in delipidated apo-B100, the protein moiety of LDL, that bind the negatively charged proteoglycans. To determine which of these sites is functional on the surface of LDL particles, we analyzed the proteoglycan-binding activity of recombinant human LDL isolated from transgenic mice. Substitution of neutral amino acids for the basic amino acids residues in site B (residues 3359-3369) abolished both the receptor-binding and the proteoglycan-binding activities of the recombinant LDL. Chemical modification of the remaining basic residues caused only a marginal further reduction in proteoglycan binding, indicating that site B is the primary proteoglycan-binding site of LDL. Although site B was essential for normal receptor-binding and proteoglycan-binding activities, these activities could be separated in recombinant LDL containing single-point mutation. Recombinant LDL with a K3363E mutation, in which a glutamic acid had been inserted into the basic cluster RKR in site B, had normal receptor binding but interacted defectively with proteoglycans; in contrast, another mutant LDL, R3500Q, displayed defective receptor binding but interacted normally with proteoglycans. LDL with normal receptor-binding activity but with severely impaired proteoglycan binding will be a unique resource for analyzing the importance of LDL- proteoglycan interaction in atherogenesis. If the subendothelial retention of LDL by proteoglycans is the initial event in early atherosclerosis, then LDL with defective proteoglycan binding may have little or no atherogenic potential.     

The pyrokinin/ pheromone biosynthesis-activating neuropeptide (PBAN) family of peptides and their receptors in Insecta: evolutionary trace indicates potential receptor ligand-binding domains

The pyrokinin/pheromone biosynthesis-activating neuropeptide (PBAN) family of G-protein-coupled receptors and their ligands have been identified in various insects. Physiological functions of pyrokinin peptides include muscle contraction, whereas PBAN regulates, among other functions, pheromone production in moths which indicates the pleiotropic nature of these peptides. Based on the alignment of annotated genomic sequences, the pyrokinin/PBAN family of receptors have similarity with the corresponding structures of the capa or periviscerokinin receptors of insects and the neuromedin U receptors of vertebrates. In our study, evolutionary trace (ET) analysis on the insect receptor sequences was conducted to predict the putative ligand recognition and binding sites. The ET analysis of four class-specific receptors indicated several amino acid residues that are conserved in the transmembrane domains. The receptor extracellular domains exhibit several class-specific amino acid residues, which could indicate putative domains for activation of these receptors by ligand recognition and binding.     

Crystal Structure of HLA-DR2 (DRA*0101, DRB1*1501) Complexed with a Peptide from Human Myelin Basic Protein

Susceptibility to multiple sclerosis is associated with the human histocompatibility leukocyte antigen (HLA)-DR2 (DRB1*1501) haplotype. The structure of HLA-DR2 was determined with a bound peptide from human myelin basic protein (MBP) that is immunodominant for human MBP-specific T cells. Residues of MBP peptide that are important for T cell receptor recognition are prominent, solvent exposed residues in the crystal structure. A distinguishing feature of the HLA-DR2 peptide binding site is a large, primarily hydrophobic P4 pocket that accommodates a phenylalanine of the MBP peptide. The necessary space for this aromatic side chain is created by an alanine at the polymorphic DRβ 71 position. These features make the P4 pocket of HLA-DR2 distinct from DR molecules associated with other autoimmune diseases.     

Structural aspects of protein kinase control-role of conformational flexibility

Protein kinases catalyze the phosphotransfer reaction fundamental to most signaling and regulatory processes in the eukaryotic cell. Absolute control of individual protein kinase activity is, therefore, of utmost importance to signaling fidelity in the cell. Mechanisms for activity modulation, including complete and reversible inactivation, have been shown by crystal structures of many active and inactive protein kinases. The structures of inactivated kinases, compared with those of active and catalytically competent kinases such as the protein kinase A catalytic subunit, highlight recurring structural alterations among a set of elements of the catalytic kinase core. These 'activity modulation sites' apparently comprise the principal evolved mechanisms for control of enzyme activity in the catalytic domain. In combination, they enable diverse physiological regulatory mechanisms operative for most protein kinases. Identification and characterization of these sites should impact strategies for discovery and design of target-specific therapeutic drugs as the range of structural variations for specific kinases becomes known. The principle site, the ATP-binding pocket, is the target of many physiological regulators and also most experimental or therapeutic inhibitors, which typically block it in a competitive or allosteric fashion. Co-crystallization studies with protein kinase A and other kinases have revealed binding features of several classes of protein kinase inhibitors. Ligand-induced structural changes are common and tend to optimize buried surface areas. The ability to optimize binding energies arising from the hydrophobic effect creates a logarithmic dependence of binding energy on buried surface areas. Exceptions to this rule arise for specific inhibitor classes, and possibly also as artifacts of structure determination.