Anchor residues in protein-protein interactions

We show that the mechanism for molecular recognition requires one of the interacting proteins, usually the smaller of the two, to anchor a specific side chain in a structurally constrained binding groove of the other protein, providing a steric constraint that helps to stabilize a native-like bound intermediate. We identify the anchor residues in 39 protein-protein complexes and verify that, even in the absence of their interacting partners, the anchor side chains are found in conformations similar to those observed in the bound complex. These ready-made recognition motifs correspond to surface side chains that bury the largest solvent-accessible surface area after forming the complex (> or =100 A2). The existence of such anchors implies that binding pathways can avoid kinetically costly structural rearrangements at the core of the binding interface, allowing for a relatively smooth recognition process. Once anchors are docked, an induced fit process further contributes to forming the final high-affinity complex. This later stage involves flexible (solvent-exposed) side chains that latch to the encounter complex in the periphery of the binding pocket. Our results suggest that the evolutionary conservation of anchor side chains applies to the actual structure that these residues assume before the encounter complex and not just to their loci. Implications for protein docking are also discussed.     

Pulmonary vascular disease in neonates with transposition of the great arteries and intact ventricular septum.

BACKGROUND--Progressive pulmonary vascular disease in surgically unrepaired transposition of the great arteries with or without ventricular septal defect had been frequently described in the past. Occurrence of progressive pulmonary vascular disease has been reported even after atrial switch procedure done at three months of age. With the advent of neonatal surgical repair, this problem is virtually non-existent. There is a small subgroup of infants with transposition of the great arteries who show pulmonary vascular disease in the neonatal period that can adversely affect the surgical outcome. The clinico-pathological correlation in this group of patients was studied. OBSERVATIONS--Three patients, with transposition of the great arteries and intact ventricular septum, who showed histological evidence of pulmonary vascular disease in the neonatal period or early infancy are described. Two of these patients, continued to have poor systemic oxygenation despite adequate atrial communication. One patient had a close ductus arteriosus within the first two hours of birth while on prostaglandin E1 infusion. CONCLUSIONS--In the absence of left ventricular outflow tract obstruction, a poor response to atrial septostomy suggests pulmonary hypertension and pulmonary vascular disease. Antenatal constriction of the ductus arteriosus may contribute to such changes in pulmonary vasculature.     

Device Closure of a Secundum Atrial Septal Defect in a 4‐Month‐Old Infant with a Marginal Left Ventricle Following Coarctation Repair

A male infant presented at birth with severe coarctation of the aorta and marginal left ventricular and mitral valve dimensions associated with a large secundum atrial septal defect. Following successful arch repair, the left ventricle remained small with preferential left‐to‐right atrial shunting and a dilated right ventricle. Clinically, the infant continued with tachypnea, poor feeding, and failure to thrive. At 4 months of age, the defect was closed with an Amplatzer Atrial Septal Occluder which resulted in immediate left ventricular cavity enlargement and clinical improvement.     

Pulmonary atresia with intact ventricular septum: range of morphology in a population-based study

OBJECTIVES: We describe the morphologic variability in pulmonary atresia with intact ventricular septum (PAIVS) within a population-based study. BACKGROUND: An uncommon disease, PAIVS shows considerable morphologic heterogeneity. Clinical reports, based mostly on small samples of patients, may not reflect the true spectrum of pathology of this condition. We have studied the entire range of morphology in a prospective population-based study of patients over a five-year period (1991 to 1995). METHODS; As part of the United Kingdom and Ireland Collaborative Study of PAIVS, all 18 pediatric cardiac centers were visited by a single investigator. Morphologic features of each case were determined by direct review of the echocardiograms and angiocardiograms, from surgical and autopsy reports, and by review of pathology specimens where available. RESULTS: Among 183 live-born infants, atresia was valvar (membranous) in 74.7% and muscular in 25.3%. Muscular obliteration of the apical trabecular cavity, and in some cases its infundibulum, resulted in "bipartite" right ventricle (RV) in 33.6%, and a "unipartite" chamber in 7.7%. The remaining 58.7% had "tripartite" morphology. Coronary arterial abnormalities were identified in 45.8%, including arterial stenoses, interruptions and ectasia in 7.6%. Ebstein's malformation coexisted in 18 patients. Median tricuspid valvar size and RV inlet Z-scores were -5.2 and -5.1, respectively. CONCLUSIONS: This study provides unique data on the diverse pathology of PAIVS in an unselected population. This will help determine if published reports reflect the true spectrum of pathology of the condition.     

Continuous efficacy of etanercept in severe and advanced ankylosing spondylitis: results from a 12-week open-label extension of the SPINE study

Objective. To evaluate the longer-term efficacy of etanercept in patients with severe and advanced active AS. Methods. Seventy-seven patients who completed the randomized, double-blind, placebo-controlled 12-week SPINE study enrolled in a 12-week open-label extension and received s.c. etanercept 50?mg once weekly. The etanercept/etanercept group received a total of 24 weeks treatment with etanercept (n?=?38); the placebo/etanercept group received placebo during the double-blind study then 12 weeks' etanercept treatment during the open-label extension (n?=?39). Results. At the end of the open-label extension, BASDAI scores in the etanercept/etanercept group had further decreased beyond reductions observed during the double-blind study [mean (s.d.) change from baseline -37.6 (22.4) at end of extension vs -27.4 (23.8) at end of double-blind study]. Mean (s.d.) BASDAI scores also improved in the placebo/etanercept group once switched to etanercept [-28.6 (24.3) vs -15.0 (20.0)]. Similar trends were observed in BASFI and BASMI scores. In the placebo/etanercept group, total back pain decreased to similar levels achieved in the etanercept group in the double-blind study. Pain levels continued to decrease with longer-term etanercept therapy in the etanercept/etanercept group. Conclusion. Despite the improvements in symptoms and inflammatory markers observed shortly after initiation of once-weekly etanercept, there was no notable plateauing effect on patient-reported outcomes. Indeed, signs and symptoms of severe and advanced active AS continued to improve after up to 24 weeks, treatment with etanercept. Trial registration: ClinicalTrials.gov, http://clinicaltrials.gov/ct2/home, NCT00420238.