Structural and biochemical studies on multi-subunit protein complexes: Brucella 26kDa immunogenic protein and chromatin assembly factor-1

Abstract

Proteins with tertiary structure assemble into quaternary complexes to carry out their cellular functions. Therefore, to understand the mechanisms of the quaternary complexes, it is important to elucidate their molecular features. In this study, the molecular features of two distinct multi-subunit protein complexes are investigated. First, the crystal structure of Brucella 26kDa Immunogenic protein (BP26) was determined revealing that sixteen molecules of BP26 form a novel channel-like structure. The crystal structure followed by biochemical and electron microscopy (EM) studies indicates that the proteins with SIMPL domain including BP26, LpqG, and IRAK1BP1 generally form multimeric structures. Second, I reconstituted Chromatin Assembly Factor-1 (CAF-1) with Asf1-H3-H4, and investigated the molecular interaction among these proteins by biochemical and EM approaches, delineating the complex formation of CAF-1 and Asf1-H3-H4. This study provides platforms to understand the molecular mechanism of the quaternary protein complexes: BP26 and CAF-1.