Department of Biology, University of Rochester, Rochester, NY 14627.
Mass Spectrometry Resource Laboratory, University of Rochester Medical Center, Rochester, NY 14627.
Proc Natl Acad Sci U S A. 2024 Nov 12;121(46):e2403880121. doi: 10.1073/pnas.2403880121. Epub 2024 Nov 5.
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 α-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 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.
在细胞内，蛋白质结合的蛋氨酸可以通过化学或酶促氧化，随后被蛋氨酸亚砜还原酶（Msr）还原。蛋氨酸氧化可导致结构损伤，或作为酶功能调节的基础。除了参与氧化还原反应外，蛋氨酸作为翻译蛋白的起始残基发挥重要作用，它们的α-氨基通常通过甲酰化或乙酰化修饰。在这里，我们研究了起始蛋氨酸的甲酰化和乙酰化如何影响其氧化和还原的倾向。我们表明，在体外，N 端蛋氨酸残基特别容易发生化学氧化，其甲酰化或乙酰化修饰极大地增强了 MsrA 和 MsrB 随后对其进行酶还原的能力。一致地，在体内敲除 中的甲硫氨酰-tRNA 甲酰基转移酶（MTF）会增加合成蛋白中氧化蛋氨酸的普遍性。我们表明，甲酰化起始蛋氨酸的氧化在一定程度上是有害的，因为它会阻碍随后由肽脱甲酰酶（PDF）进行的脱甲酰化和由蛋氨酰氨基肽酶（MAP）进行的水解。因此，通过促进其还原，甲酰化减轻了氧化起始蛋氨酸的错误加工。
