Solution structure of an EGF pair (EGF34) from vitamin K-dependent protein S
[PROS_HUMAN] Defects in PROS1 are the cause of thrombophilia due to protein S deficiency, autosomal dominant (THPH5) [MIM:612336]. A hemostatic disorder characterized by impaired regulation of blood coagulation and a tendency to recurrent venous thrombosis. However, many adults with heterozygous disease may be asymptomatic. Based on the plasma levels of total and free PROS1 antigen as well as the serine protease-activated protein C cofactor activity, three types of PROS1D have been described: type I, characterized by reduced total and free PROS1 antigen levels together with reduced anticoagulant activity; type III, in which only free PROS1 antigen and PROS1 activity levels are reduced; and the rare type II which is characterized by normal concentrations of both total and free PROS1 antigen, but low cofactor activity. [:]                        Defects in PROS1 are the cause of thrombophilia due to protein S deficiency, autosomal recessive (THPH6) [MIM:614514]. A very rare and severe hematologic disorder resulting in thrombosis and secondary hemorrhage usually beginning in early infancy. Some affected individuals develop neonatal purpura fulminans, multifocal thrombosis, or intracranial hemorrhage.
[PROS_HUMAN] Anticoagulant plasma protein; it is a cofactor to activated protein C in the degradation of coagulation factors Va and VIIIa. It helps to prevent coagulation and stimulating fibrinolysis.
Publication Abstract from PubMed
Vitamin K-dependent protein S is a cofactor of activated protein C, a serine protease that regulates blood coagulation. Deficiency of protein S can cause venous thrombosis. Protein S has four EGF domains in tandem; domains 2-4 bind calcium with high affinity whereas domains 1-2 mediate interaction with activated protein C. We have now solved the solution structure of the EGF3-4 fragment of protein S. The linker between the two domains is similar to what has been observed in other calcium-binding EGF domains where it provides an extended conformation. Interestingly, a disagreement between NOE and RDC data revealed a conformational heterogeneity within EGF3 due to a hinge-like motion around Glu186 in the Cys-Glu-Cys sequence, the only point in the domain where flexibility is allowed. The dominant, bent conformation of EGF3 in the pair has no precedent among calcium-binding EGF domains. It is characterized by a change in the psi angle of Glu186 from 160 degrees +/- 40 degrees , as seen in ten other EGF domains, to approximately 0 degrees +/- 15 degrees . NOESY data suggest that Tyr193, a residue not conserved in other calcium-binding EGF domains (except in the homologue Gas6), induces the unique fold of EGF3. However, SAXS data, obtained on EGF1-4 and EGF2-4, showed a dominant, extended conformation in these fragments. This may be due to a counterproductive domain-domain interaction between EGF2 and EGF4 if EGF3 is in a bent conformation. We speculate that the ability of EGF3 to adopt different conformations may be of functional significance in protein-protein interactions involving protein S.
Solution structure of the Ca2+-Binding EGF3-4 pair from vitamin K-dependent protein S: identification of an unusual fold in EGF3.,Drakenberg T, Ghasriani H, Thulin E, Thamlitz AM, Muranyi A, Annila A, Stenflo J Biochemistry. 2005 Jun 21;44(24):8782-9. PMID:15952784
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.