title: Ubiquitin-like small archaeal modifier proteins (SAMPs) in Haloferax volcanii.
abstract: Archaea, one of three major evolutionary lineages of life, encode proteasomes highly related to those of eukaryotes. In contrast, archaeal ubiquitin-like proteins are less conserved and not known to function in protein conjugation. This has complicated our understanding of the origins of ubiquitination and its connection to proteasomes. Here we report two small archaeal modifier proteins, SAMP1 and SAMP2, with a beta-grasp fold and carboxy-terminal diglycine motif similar to ubiquitin, that form protein conjugates in the archaeon Haloferax volcanii. The levels of SAMP-conjugates were altered by nitrogen-limitation and proteasomal gene knockout and spanned various functions including components of the Urm1 pathway. LC-MS/MS-based collision-induced dissociation demonstrated isopeptide bonds between the C-terminal glycine of SAMP2 and the epsilon-amino group of lysines from a number of protein targets and Lys 58 of SAMP2 itself, revealing poly-SAMP chains. The widespread distribution and diversity of pathways modified by SAMPylation suggest that this type of protein conjugation is central to the archaeal lineage.
authors.affiliation: Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Humbard
authors.forename: Hugo V
authors.initials: HV
authors.lastname: Miranda
authors.forename: Jae-Min
authors.initials: JM
authors.lastname: Lim
authors.forename: David J
authors.initials: DJ
authors.lastname: Krause
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Pritz
authors.forename: Guangyin
authors.initials: G
authors.lastname: Zhou
authors.forename: Sixue
authors.initials: S
authors.lastname: Chen
authors.forename: Lance
authors.initials: L
authors.lastname: Wells
authors.forename: Julie A
authors.initials: JA
authors.lastname: Maupin-Furlow
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism*; D017353:Gene Deletion; D006033:Glycylglycine / Q000378:metabolism; D019622:Haloferax volcanii / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013455:Sulfur / Q000378:metabolism; D054875:Ubiquitination; D014452:Ubiquitins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D019843:Archaeal Proteins; D014452:Ubiquitins; D006033:Glycylglycine; D013455:Sulfur; D046988:Proteasome Endopeptidase Complex; D009584:Nitrogen