Formylation facilitates the reduction of oxidized initiator methionines

• 成果类型: Article
• 署名作者: Tan, Ruiyue; Hoare, Margaret; Bellomio, Philip; Broas, Sarah; Camacho, Konttessa; Swovick, Kyle; Welle, Kevin A.; Hryhorenko, Jennifer R.; Ghaemmaghami, Sina
• 署名单位: University of Rochester; University of Rochester
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11322
• DOI: 10.1073/pnas.2403880121
• 发表日期: 2024-11-12
• 关键词: n-terminal acetylation; sulfoxide-reductase; escherichia-coli; catalytic mechanism; kinetic characterization; antioxidant defense; mass-spectrometry; oxidation; proteins; deformylase

摘要

Within a cell, protein- bound methionines can be chemically or enzymatically oxidized, and subsequently reduced by methionine sulfoxide reductases (Msrs). Methionine oxidation can result in structural damage or be the basis of functional regulation of enzymes. In addition to participating in redox reactions, methionines play an important role as the initiator residue of translated proteins where they are commonly modified at their alpha- amine group by formylation or acetylation. Here, we investigated how formylation and acetylation of initiator methionines impact their propensity for oxidation and reduction. We show that in vitro, N- terminal methionine residues are particularly prone to chemical oxidation and that their modification by formylation or acetylation greatly enhances their subsequent enzymatic reduction by MsrA and MsrB. Concordantly, in vivo ablation of methionyl- tRNA formyltransferase (MTF) in Escherichia coli increases the prevalence of oxidized methionines within synthesized proteins. We show that oxidation of formylated initiator methionines is detrimental in part because it obstructs their ensuing deformylation by peptide deformylase (PDF) and hydrolysis by methionyl aminopeptidase (MAP). Thus, by facilitating their reduction, formylation mitigates the misprocessing of oxidized initiator methionines.