PDBsum entry 4qpy

Protein binding

PDB id: 4qpy

Contents

Protein chains

131 a.a.

Waters ×112

References listed in PDB file

Key reference

• Title: Structures of c1q-Like proteins reveal unique features among the c1q/tnf superfamily.
• Authors: S.Ressl, B.K.Vu, S.Vivona, D.C.Martinelli, T.C.Südhof, A.T.Brunger.
• Ref.: Structure, 2015, 23, 688-699. [DOI no: 10.1016/j.str.2015.01.019]
• PubMed id: 25752542

Abstract

C1q-like (C1QL) -1, -2, and -3 proteins are encoded by homologous genes that are highly expressed in brain. C1QLs bind to brain-specific angiogenesis inhibitor 3 (BAI3), an adhesion-type G-protein coupled receptor that may regulate dendritic morphology by organizing actin filaments. To begin to understand the function of C1QLs, we determined high-resolution crystal structures of the globular C1q-domains of C1QL1, C1QL2, and C1QL3. Each structure is a trimer, with each protomer forming a jelly-roll fold consisting of 10 β strands. Moreover, C1QL trimers may assemble into higher-order oligomers similar to adiponectin and contain four Ca(2+)-binding sites along the trimeric symmetry axis, as well as additional surface Ca(2+)-binding sites. Mutation of Ca(2+)-coordinating residues along the trimeric symmetry axis lowered the Ca(2+)-binding affinity and protein stability. Our results reveal unique structural features of C1QLs among C1q/TNF superfamily proteins that may be associated with their specific brain functions.