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FIFTH EGF-LIKE DOMAIN OF THROMBOMODULIN (TMEGF5), NMR, 14 STRUCTURES
Structural highlights
DiseaseTRBM_HUMAN Defects in THBD are the cause of thrombophilia due to thrombomodulin defect (THPH12) [MIM:614486. A hemostatic disorder characterized by a tendency to thrombosis.[1] [2] [3] Defects in THBD are a cause of susceptibility to hemolytic uremic syndrome atypical type 6 (AHUS6) [MIM:612926. An atypical form of hemolytic uremic syndrome. It is a complex genetic disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, renal failure and absence of episodes of enterocolitis and diarrhea. In contrast to typical hemolytic uremic syndrome, atypical forms have a poorer prognosis, with higher death rates and frequent progression to end-stage renal disease. Note=Susceptibility to the development of atypical hemolytic uremic syndrome can be conferred by mutations in various components of or regulatory factors in the complement cascade system. Other genes may play a role in modifying the phenotype.[4] [5] FunctionTRBM_HUMAN Thrombomodulin is a specific endothelial cell receptor that forms a 1:1 stoichiometric complex with thrombin. This complex is responsible for the conversion of protein C to the activated protein C (protein Ca). Once evolved, protein Ca scissions the activated cofactors of the coagulation mechanism, factor Va and factor VIIIa, and thereby reduces the amount of thrombin generated. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe structure of the fifth EGF-like domain (residues Q387 to E426) of thrombomodulin (TMEGF5) has been determined by two-dimensional NMR. TMEGF5 binds to thrombin with a Ki of 1.9 microM and has been shown to have a novel disulfide bonding pattern in a fully active fragment of TM. In EGF, the disulfide bonding pattern is (1-3,2-4, 5-6), while TMEGF5 has an uncrossed (1-2,3-4,5-6) pattern. The structure of this novel domain, determined from 483 NOE-derived distance restraints, appears to have diverged from the common EGF-like structure. Superposition of the 14 lowest-energy structures of TMEGF5 gives an overall r.m.s.d. of 1.09 A for the backbone atoms. The central two-stranded beta-sheet common to all EGF-like domains is not present in TMEGF5. The A loop, residues C390 to C395, is twisted away from interacting with the B loop, residues C399 to C407, as in EGF, and is close to the C loop, residues C409 to C421. This twist causes the N and C termini to be closer together in TMEGF5 than in EGF. Most of the residues that are important for activity lie on one face of the molecule, which is likely to be the thrombin-binding surface of the domain. The structure of the C loop within the domain, which is a beta-hairpin similar to EGF, is similar to the structure of a synthetic version of the loop bound to thrombin as determined by transferred NOE experiments. Despite the similarity in the structures of the loops, the residues immediately following C421 are in different positions in the two structures suggesting that these "tail" residues may change conformation upon thrombin binding. Structure of the fifth EGF-like domain of thrombomodulin: An EGF-like domain with a novel disulfide-bonding pattern.,Sampoli Benitez BA, Hunter MJ, Meininger DP, Komives EA J Mol Biol. 1997 Nov 7;273(4):913-26. PMID:9367781[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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