1apq

<StructureSection load='1apq' size='340' side='right'caption='[[1apq]], [[NMR_Ensembles_of_Models | 19 NMR models]]' scene=''>

<table><tr><td colspan='2'>[[1apq]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Human Human]. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1APQ OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1APQ FirstGlance]. <br>

</td></tr><tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[https://en.wikipedia.org/wiki/Complement_subcomponent_C1r Complement subcomponent C1r], with EC number [https://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.21.41 3.4.21.41] </span></td></tr>

[[https://www.uniprot.org/uniprot/C1R_HUMAN C1R_HUMAN]] C1r B chain is a serine protease that combines with C1q and C1s to form C1, the first component of the classical pathway of the complement system.

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== Publication Abstract from PubMed ==

The calcium-dependent interaction between C1r and C1s, the two homologous serine proteases of the first component of human complement C1, is mediated by their N-terminal regions. The latter comprise an epidermal growth factor (EGF)-like module exhibiting the consensus sequence characteristic of Ca(2+)-binding EGF modules, surrounded by two CUB modules. Due to its Ca2+ binding ability, the C1r EGF-like module (C1r-EGF) is supposed to participate in the C1r-C1s interaction. An additional interesting feature of C1r-EGF is the unusually large loop connecting the first two conserved cysteine residues. The solution structure of synthetic C1r-EGF (residues 123-175) has been determined using nuclear magnetic resonance and combined simulated annealing-restrained molecular dynamics calculations. The resulting family of 19 structures is characterized by a well-ordered C-terminal part (residues Cys 144-Ala174) with a backbone rmsd of 0.7 A and a disordered N-terminal, including the large loop between the first two cysteines (Cys129 and Cys144). This loop is known to be surface exposed and may be expected to participate in domain-domain or protein-protein interactions. In its C-terminal part, C1r-EGF possesses the characteristic EGF fold with a major and a minor beta-sheet. The latter comprises a beta-bulge, and comparison with other EGF-like modules reveals the existence of two distinct structural and sequential motifs in the bulged part. Additional experiments in the presence of 80 mM Ca2+ did not show significant structural variation of C1r-EGF, in keeping with previous observations on blood-clotting factors IX and X.

Solution structure of the epidermal growth factor (EGF)-like module of human complement protease C1r, an atypical member of the EGF family.,Bersch B, Hernandez JF, Marion D, Arlaud GJ Biochemistry. 1998 Feb 3;37(5):1204-14. PMID:9477945<ref>PMID:9477945</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

<references/>

[[Category: Complement subcomponent C1r]]

[[Category: Human]]

[[Category: Arlaud, G J]]

[[Category: Bersch, B]]

[[Category: Hernandez, J F]]

[[Category: Marion, D]]

[[Category: Serine protease]]