Archaeal Flagella

Abstract

Abstract The archaeal flagellum is a unique, ‘tail‐like’ structure used for motility by single‐celled organisms belonging to the domain Archaea. These intricate protein assemblies extend from the cell surface, rotating to generate thrust that propels the organism. Although archaeal flagella are functionally similar to the flagella found on bacteria, they differ significantly in structure and presumed mode of assembly. Key concepts The student will learn: Although functionally similar to bacterial flagella, archaeal flagella are unique motility structures in terms of their structure and assembly. The structure of the flagellum can be divided into three distinct components: the filament, hook and anchoring structure. Each of these components is constructed of specific proteins either encoded by genes residing within flagellar operons or of currently unknown genes. Assembly of the archaeal flagellum, which lacks the internal channel found in bacterial flagella, is thus believed to occur via incorporation of protein subunits at the base of the structure after they undergo the necessary posttranslational modifications of signal peptide cleavage and glycan addition. Archaea use this motility apparatus in combination with chemotaxis systems to bias their direction of movement towards environmental conditions more favourable for cell growth.