Elucidation of Protein‐Protein Interactions in the Flagella Structure and Characterization of the Glycosylation State of Flagellin Subunits of the Methanogenic Archaeon Methanococcus Maripaludis

Abstract

The archaeal flagellum is a rotating prokaryotic motility apparatus used for swimming motility and adhesion; however, it is more closely related to the bacterial type IV pilus system than its bacterial namesake. Methanococcus maripaludis is a highly flagellated, obligately anaerobic methanogen and is used as the archaeal model system during this study. The identified structural genes of the archaeal flagella are transcribed by a single fla operon; however, the interactions between the majority of the Fla proteins has yet to be elucidated. In this work, several techniques were attempted to determine the protein-protein interactions between Fla proteins, including membrane fractionation experiments and in vitro dimerization assays. Evidence from these experiments suggests that two proteins, FlaC and FlaE, have the ability to self-associate. The M. maripaludis flagella system is also used as a model for the study of the N-linked glycosylation pathway in the domain, due to the presence of a tetrasaccharide N-linked to flagellin monomers. Previous work has identified several of the processes involved in the assembly of this glycan, including glycosyltransferases, the oligosaccharide transferase and several of the key components involved in the biosynthesis of the sugar residue precursors. However, many of the enzymes responsible for biochemical modifications to the sugar residues remain to be determined. The operon structure of the genes between mmp1080 and mmp1095 was experimentally confirmed using RT-PCR, and each of the operons contains at least one gene involved in the biosynthesis of the N-linked glycan. In-frame deletions of genes in this region were characterized for effects on the N-linked glycan. Evidence suggests that Mmp1082 and Mmp1083 are acting in conjunction with Mmp1081 in the addition of an acetamidino functional group to the third sugar residue. Mmp1085 was determined to be a methyltransferase responsiblefor the methylation of the terminal sugar residue. Additionally, Mmp1087 and Mmp1094 were identified as potentially having an effect on the glycan. Though this work, the breadth of knowledge in regards to both the archaeal flagella and the N-linked glycosylation process in the domain has been increased.