title: Proteome targets of ubiquitin-like samp1ylation are associated with sulfur metabolism and oxidative stress in Haloferax volcanii.
abstract: Small archeal modifier proteins (SAMPs) are related to ubiquitin in tertiary structure and in their isopeptide linkage to substrate proteins. SAMPs also function in sulfur mobilization to form biomolecules such as molybdopterin and thiolated tRNA. While SAMP1 is essential for anaerobic growth and covalently attached to lysine residues of its molybdopterin synthase partner MoaE (K240 and K247), the full diversity of proteins modified by samp1ylation is not known. Here, we expand the knowledge of proteins isopeptide linked to SAMP1. LC-MS/MS analysis of -Gly-Gly signatures derived from SAMP1 S85R conjugates cleaved with trypsin was used to detect sites of sampylation (23 lysine residues) that mapped to 11 target proteins. Many of the identified target proteins were associated with sulfur metabolism and oxidative stress including MoaE, SAMP-activating E1 enzyme (UbaA), methionine sulfoxide reductase homologs (MsrA and MsrB), and the Fe-S assembly protein SufB. Several proteins were found to have multiple sites of samp1ylation, and the isopeptide linkage at SAMP3 lysines (K18, K55, and K62) revealed hetero-SAMP chain topologies. Follow-up affinity purification of selected protein targets (UbaA and MoaE) confirmed the LC-MS/MS results. 3D homology modeling suggested sampy1ylation is autoregulatory in inhibiting the activity of its protein partners (UbaA and MoaE), while occurring on the surface of some protein targets, such as SufB and MsrA/B. Overall, we provide evidence that SAMP1 is a ubiquitin-like protein modifier that is relatively specific in tagging its protein partners as well as proteins associated with oxidative stress response.
authors: Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, USA.
authors: Swathi
authors: S
authors: Dantuluri
authors: Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, USA.|College of Forestry, Northwest A & F University, Yangling, Shaanxi, P. R. China.
authors: Yifei
authors: Y
authors: Wu
authors: Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, USA.
authors: Nathaniel L
authors: NL
authors: Hepowit
authors: College of Forestry, Northwest A & F University, Yangling, Shaanxi, P. R. China.
authors: Hui
authors: H
authors: Chen
authors: Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, USA.|Department of Biology, College of Liberal Arts and Sciences, University of Florida, Gainesville, USA.|Genetics Institute, University of Florida, Gainesville, USA.
authors: Sixue
authors: S
authors: Chen
authors: Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, USA.|Genetics Institute, University of Florida, Gainesville, USA.
authors: Julie A
authors: JA
authors: Maupin-Furlow
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism*; D019622:Haloferax volcanii / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D018384:Oxidative Stress / Q000502:physiology*; D020543:Proteome / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D013455:Sulfur / Q000737:chemistry / Q000378:metabolism*; D025801:Ubiquitin
chemical_list: D019843:Archaeal Proteins; D020543:Proteome; D025801:Ubiquitin; D013455:Sulfur
keywords: Archaea; Microbiology; Oxidative stress; Sampylation; Sulfur mobilization; Ubiquitin