Three-Dimensional Structure of the 54-Kda Subunit of the Chloroplast Signal Recognition Particle using Molecular Modeling

Abstract

The chloroplast signal recognition particle is a heterodimeric complex of the 54kDa cytosolic signal recognition particle homologue (cpSRP54), and a novel 43kDa subunit (cpSRP43). While a nearly complete three-dimensional structure of cpSRP43 has been obtained, no structure is yet available for cpSRP54. The three-dimensional structure for cpSRP54 could provide valuable information for the rationalization of the extensive information already available regarding its function, and in the understanding of the as yet undetermined mechanism of light harvesting chlorophyll binding protein's (LHCP) insertion into the thylakoid membrane. In this study, we developed an in silico, three-dimensional structural model of cpsRP54 using a combination of homology modeling, de novo structure prediction and molecular dynamics simulation. The resulting structure is consistent with the known properties of the protein and sheds new light on some of the mechanistic details of its functioning.