Novel Binding Partners for CCT and PhLP1 Suggest a Common Folding Mechanism for WD40 Proteins with a 7-Bladed Beta-Propeller Structure

Wai Shun Mak,Tsz Yin Chan,Tsz Ming Tsang,Georgi L Lukov

doi:10.3390/proteomes9040040

Abstract

This study investigates whether selected WD40 proteins with a 7-bladed β-propeller structure, similar to that of the β subunit of the G protein heterotrimer, interact with the cytosolic chaperonin CCT and its known binding partner, PhLP1. Previous studies have shown that CCT is required for the folding of the Gβ subunit and other WD40 proteins. The role of PhLP1 in the folding of Gβ has also been established, but it is unknown if PhLP1 assists in the folding of other Gβ-like proteins. The binding of three Gβ-like proteins, TBL2, MLST8 and CDC20, to CCT and PhLP1, was demonstrated in this study. Co-immunoprecipitation assays identified one novel binding partner for CCT and three new interactors for PhLP1. All three of the studied proteins interact with CCT and PhLP1, suggesting that these proteins may have a folding machinery in common with that of Gβ and that the well-established Gβ folding mechanism may have significantly broader biological implications than previously thought. These findings contribute to continuous efforts to determine common traits and unique differences in the folding mechanism of the WD40 β-propeller protein family, and the role PhLP1 has in this process.

Highlights

IntroductionThe rings form a folding chamber in the middle of the complex, which is large enough to enclose a 70 kDa protein [7]
The cytosolic chaperonin containing tailless complex polypeptide 1 (TCP-1), or CCT, which is known as TRiC (TCP-1 ring complex), is a protein complex that assists in the folding of many essential cellular proteins [1,2]
The phosducin-like protein 1 (PhLP1)-Gβ complex associates with Gγ to form a stable Gβγ dimer that is ready to associate with Gα, which displaces PhLP1 and forms the complete G protein heterotrimer [11]

Summary

Introduction

The rings form a folding chamber in the middle of the complex, which is large enough to enclose a 70 kDa protein [7]. PhLP1 binds the CCT-Gβ complex, stabilizes the mature fold of Gβ, and triggers its release from CCT in a fully folded form [11,12]. The PhLP1-Gβ complex associates with Gγ to form a stable Gβγ dimer that is ready to associate with Gα, which displaces PhLP1 and forms the complete G protein heterotrimer [11]. It is unknown if other CCT substrates require the assistance of PhLP1 for their proper folding

Objectives

Methods

Results

Discussion

Conclusion