Structural Characterization of Calcineurin B Homologous Protein 1

Youichi Naoe,Kyouhei Arita,Hiroshi Hashimoto,Hiroshi Kanazawa,Mamoru Sato,Toshiyuki Shimizu

doi:10.1074/jbc.m503390200

Abstract

Calcineurin B homologous protein 1 (CHP1), also known as p22, is a calcium-binding EF-hand protein that plays a role in membrane trafficking. It binds to multiple effector proteins, including Na(+)/H(+) exchangers, a serine/threonine kinase, and calcineurin, potentially modulating their function. The crystal structure of calcium-bound CHP1 from rat has been determined at 2.2 Angstroms of resolution. The molecule has a compact alpha-helical structure containing four EF-hands. The overall folding topology of the protein is similar to that of the regulatory B subunit of calcineurin and to that of calcium- and integrin-binding protein. The calcium ion is coordinated in typical fashion in the third and fourth EF-hands, but the first and second EF-hands contain no calcium ion. The first EF-hand is maintained by internal interactions, and the second EF-hand is stabilized by hydrophobic interactions. CHP1 contains a hydrophobic pocket on the opposite side of the protein to the EF-hands that has been implicated in ligand binding.

Highlights

Japan Society of the Promotion of Science (JSPS)
Calcineurin B homologous protein 1 (CHP1) binds to the catalytic A subunit of calcineurin (CNA) directly and inhibits its phosphatase activity, suggesting that CHP1 is an endogenous inhibitor of calcineurin
Myristoylation does not significantly affect the affinity for calcium [5] nor is it required for the interaction of CHP1 with NHE1 [3] or death-associated protein kinase-related apoptosisinducing protein kinase 2 (DRAK2) [10]

Summary

Introduction

Japan Society of the Promotion of Science (JSPS) A mutation of CHP1, in which the displays lacked calcium-binding affinity, has a significantly reduced Naϩ/Hϩ exchange activity [5]. Another isoform of CHP1, referred to as CHP2, sharing a 61% amino acid identity with CHP1, has been reported [6, 7]. CHP1 interacts with KIF1B␤2 and other members of the KIF1B family of microtubule-dependent motor proteins in a calcium-dependent manner [11]. Myristoylation does not significantly affect the affinity for calcium [5] nor is it required for the interaction of CHP1 with NHE1 [3] or DRAK2 [10]. CHP1 predominantly localizes to the cytoplasm because of two functional nuclear export signal sequences in its C terminus [14]

Methods

Results

Conclusion