title: The Haloferax volcanii FtsY homolog is critical for haloarchaeal growth but does not require the A domain.
abstract: The targeting of many Sec substrates to the membrane-associated translocation pore requires the cytoplasmic signal recognition particle (SRP). In Eukarya and Bacteria it has been shown that membrane docking of the SRP-substrate complex occurs via the universally conserved SRP receptor (Sralpha/beta and FtsY, respectively). While much has been learned about the archaeal SRP in recent years, few studies have examined archaeal Sralpha/FtsY homologs. In the present study the FtsY homolog of Haloferax volcanii was characterized in its native host. Disruption of the sole chromosomal copy of ftsY in H. volcanii was possible only under conditions where either the full-length haloarchaeal FtsY or an amino-terminally truncated version of this protein lacking the A domain, was expressed in trans. Subcellular fractionation analysis of H. volcanii ftsY deletion strains expressing either one of the complementing proteins revealed that in addition to a cytoplasmic pool, both proteins cofractionate with the haloarchaeal cytoplasmic membrane. Moreover, membrane localization of the universally conserved SRP subunit SRP54, the key binding partner of FtsY, was detected in both H. volcanii strains. These analyses suggest that the H. volcanii FtsY homolog plays a crucial role but does not require its A domain for haloarchaeal growth.
authors.affiliation: Department of Biology, University of Pennsylvania, Philadelphia 19104, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Haddad
authors.forename: R Wesley
authors.initials: RW
authors.lastname: Rose
authors.forename: Mechthild
authors.initials: M
authors.lastname: Pohlschröder
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D019622:Haloferax volcanii / Q000254:growth & development* / Q000378:metabolism; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; C087406:FtsY protein, Bacteria; D018160:Receptors, Cytoplasmic and Nuclear