title: E3-independent ubiquitination of AtMAPR/MSBP1.
abstract: AtMAPR5/MSBP1 and its homologs can be ubiquitinated in the absence of E3 ligase in in vitro ubiquitination assays. Ubiquitinated AtMAPR3, AtMAPR5/MSBP1, and AtMAPR2 were identified using LC-MS/MS. Analysis of trypsin-released signature peptides showed that this E3-independent ubiquitination of AtMAPR3, AtMAPR5/MSBP1, and AtMAPR2 was dominated by mono-ubiquitination at multiple sites. Unlike AtUBC8-type E2s, AtUBC36 was not able to transfer ubiquitin to AtMAPR2. The truncated mutants AtMAPR2Δ1-10, AtMAPR2Δ1-30, and AtMAPR2_1-73 could also be ubiquitinated. The presence of a ubiquitin-binding domain (UBD) allows proteins to be ubiquitinated independently of E3 ligases. However, AtMAPRs do not contain any known UBD. In vitro ubiquitination of AtMAPR2 observed in this study will be further studied in biochemical and physiological aspects.
authors.affiliation: Institute of Microbiology and Biochemistry, National Taiwan University, Taiwan.
authors.forename: Ai-Ling
authors.initials: AL
authors.lastname: Kao
authors.forename: Ying-Han
authors.initials: YH
authors.lastname: Lin
authors.forename: Rita P-Y
authors.initials: RP
authors.lastname: Chen
authors.forename: Yun-Yen
authors.initials: YY
authors.lastname: Huang
authors.forename: Ching-Chung
authors.initials: CC
authors.lastname: Chen
authors.forename: Chien-Chih
authors.initials: CC
authors.lastname: Yang
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; C504785:MSBP1 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases