title: N-Terminal modifications of the 19S regulatory particle subunits of the yeast proteasome.
abstract: The yeast (Saccharomyces cerevisiae) contains three N-acetyltransferases, NatA, NatB, and NatC, each of which acetylates proteins with different N-terminal regions. The 19S regulatory particle of the yeast 26S proteasome consists of 17 subunits, 12 of which are N-terminally modified. By using nat1, nat3, and mak3 deletion mutants, we found that 8 subunits, Rpt4, Rpt5, Rpt6, Rpn2, Rpn3, Rpn5, Rpn6, and Rpn8, were NatA substrates, and that 2 subunits, Rpt3 and Rpn11, were NatB substrates. Mass spectrometric analysis revealed that the initiator Met of Rpt2 precursor polypeptide was processed and a part of the mature Rpt2 was N-myristoylated. The crude extracts from the normal strain and the nat1 deletion mutant were similar in chymotrypsin-like activity in the presence of ATP in vitro and in the accumulation level of the 26S proteasome. These characteristics were different from those of the 20S proteasome: the chymotrypsin-like activity and accumulation level of 20S proteasome were appreciably higher from the nat1 deletion mutant than from the normal strain.
authors.affiliation: Kihara Institute for Biological Research/Graduate School of Integrated Science, Yokohama City University, Maioka 641-12, Totsuka, Yokohama, Japan
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Kimura
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Saeki
authors.forename: Hideyoshi
authors.initials: H
authors.lastname: Yokosawa
authors.forename: Bogdan
authors.initials: B
authors.lastname: Polevoda
authors.forename: Fred
authors.initials: F
authors.lastname: Sherman
authors.forename: Hisashi
authors.initials: H
authors.lastname: Hirano
mesh_terms: D000107:Acetylation; D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D002918:Chymotrypsin / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D012335:RNA, Ribosomal / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D009097:Multienzyme Complexes; D012335:RNA, Ribosomal; C097639:RNA, ribosomal, 19S; D000255:Adenosine Triphosphate; D000123:Acetyltransferases; D002918:Chymotrypsin; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex