The ithree institute, University of Technology Sydney, PO Box 123, Broadway, NSW, 2007, Australia.
Proteomics Core Facility, University of Technology Sydney, PO Box 123, Broadway, NSW, 2007, Australia.
Sci Rep. 2017 Sep 11;7(1):11063. doi: 10.1038/s41598-017-11296-9.
Proteolytic processing alters protein function. Here we present the first systems-wide analysis of endoproteolysis in the genome-reduced pathogen Mycoplasma hyopneumoniae. 669 N-terminal peptides from 164 proteins were identified, demonstrating that functionally diverse proteins are processed, more than half of which 75 (53%) were accessible on the cell surface. Multiple cleavage sites were characterised, but cleavage with arginine in P1 predominated. Putative functions for a subset of cleaved fragments were assigned by affinity chromatography using heparin, actin, plasminogen and fibronectin as bait. Binding affinity was correlated with the number of cleavages in a protein, indicating that novel binding motifs are exposed, and protein disorder increases, after a cleavage event. Glyceraldehyde 3-phosphate dehydrogenase was used as a model protein to demonstrate this. We define the rules governing methionine excision, show that several aminopeptidases are involved, and propose that through processing, genome-reduced organisms can expand protein function.
蛋白水解加工可改变蛋白质的功能。在这里，我们首次对基因组简化病原体猪肺炎支原体中的内肽酶进行了系统全面的分析。从 164 种蛋白质中鉴定出了 669 个 N 端肽段，这表明功能多样的蛋白质被加工，其中超过一半（75%）可在细胞表面获得。对多个切割位点进行了表征，但以精氨酸为 P1 的切割为主。使用肝素、肌动蛋白、纤溶酶原和纤维连接蛋白作为诱饵，通过亲和层析为一组切割片段分配了推定的功能。结合亲和力与蛋白质中的切割次数相关，表明在切割事件后，新的结合基序暴露，蛋白质无序度增加。甘油醛 3-磷酸脱氢酶被用作模型蛋白来证明这一点。我们定义了甲硫氨酸切除的规则，表明有几种氨肽酶参与其中，并提出通过加工，基因组简化的生物体可以扩展蛋白质的功能。
