The proteomics of N-terminal methionine cleavage
The proteomics of N-terminal methionine cleavage
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DOI：
10.1074/mcp.m600225-mcp200
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发表时间：
2006-12-01
影响因子：
7
通讯作者：
Meinnel, Thierry
中科院分区：
文献类型：
--
作者：
Frottin, Frederic;Martinez, Aude;Meinnel, Thierry
甲硫氨酸氨基肽酶（MAP）是一种广泛存在的、参与蛋白质N-末端甲硫氨酸切除的必需酶。根据普遍接受的MAP切割规则，这种酶切割所有在第二位（P1 '）残基上具有小侧链的蛋白质，但已知有许多例外。用模拟天然底物的大（> 120）相干肽阵列在体外研究了大肠杆菌MAP 1的底物特异性，并详细地进行了动力学分析。在P1'处具有瓦尔或Thr的肽比在该位置处具有Ala、Cys、Gly、Pro或Ser的肽的切割效率低得多。P2 '、P3'和P4'上的某些残基强烈减缓了反应，并且P1'上具有瓦尔和Thr的一些蛋白质无法进行Met切割。这些体外数据与862 E的数据完全一致。已知N-末端序列的大肠杆菌蛋白。发现特异性位点与其他类型的MAP，MAP 2的特异性位点相同，并且现在可以使用Met切割的专用预测工具。考虑到MAP切割和前导肽去除的规则，从注释的基因组预测所有蛋白质的N末端，并与体内获得的数据进行比较。该分析表明，显示N-Met切割的蛋白质在体内过量表达。我们的结论是，涉及前导肽裂解的蛋白质分泌比通常认为的更频繁。
Methionine aminopeptidase ( MAP) is a ubiquitous, essential enzyme involved in protein N-terminal methionine excision. According to the generally accepted cleavage rules for MAP, this enzyme cleaves all proteins with small side chains on the residue in the second position (P1'), but many exceptions are known. The substrate specificity of Escherichia coli MAP1 was studied in vitro with a large (> 120) coherent array of peptides mimicking the natural substrates and kinetically analyzed in detail. Peptides with Val or Thr at P1' were much less efficiently cleaved than those with Ala, Cys, Gly, Pro, or Ser in this position. Certain residues at P2', P3', and P4' strongly slowed the reaction, and some proteins with Val and Thr at P1' could not undergo Met cleavage. These in vitro data were fully consistent with data for 862 E. coli proteins with known N-terminal sequences in vivo. The specificity sites were found to be identical to those for the other type of MAPs, MAP2s, and a dedicated prediction tool for Met cleavage is now available. Taking into account the rules of MAP cleavage and leader peptide removal, the N termini of all proteins were predicted from the annotated genome and compared with data obtained in vivo. This analysis showed that proteins displaying N-Met cleavage are over-represented in vivo. We conclude that protein secretion involving leader peptide cleavage is more frequent than generally thought.