PDBsum entry 4rqm

Protein binding

PDB id: 4rqm

Contents

Protein chains

63 a.a.

59 a.a.

Ligands

_ZN

Waters ×40

References listed in PDB file

Key reference

• Title: Crystal structure of bicc1 sam polymer and mapping of interactions between the ciliopathy-Associated proteins bicc1, Anks3, And anks6.
• Authors: B.Rothé, C.N.Leettola, L.Leal-Esteban, D.Cascio, S.Fortier, M.Isenschmid, J.U.Bowie, D.B.Constam.
• Ref.: Structure, 2018, 26, 209. [DOI no: 10.1016/j.str.2017.12.002]
• PubMed id: 29290488

Abstract

Head-to-tail polymers of sterile alpha motifs (SAM) can scaffold large macromolecular complexes. Several SAM-domain proteins that bind each other are mutated in patients with cystic kidneys or laterality defects, including the Ankyrin (ANK) and SAM domain-containing proteins ANKS6 and ANKS3, and the RNA-binding protein Bicc1. To address how their interactions are regulated, we first determined a high-resolution crystal structure of a Bicc1-SAM polymer, revealing a canonical SAM polymer with a high degree of flexibility in the subunit interface orientations. We further mapped interactions between full-length and distinct domains of Bicc1, ANKS3, and ANKS6. Neither ANKS3 nor ANKS6 alone formed macroscopic homopolymers in vivo. However, ANKS3 recruited ANKS6 to Bicc1, and the three proteins together cooperatively generated giant macromolecular complexes. Thus, the giant assemblies are shaped by SAM domains, their flanking sequences, and SAM-independent protein-protein and protein-mRNA interactions.