1] Department of Microbiology, Monash University, Melbourne, Victoria 3800, Australia [2] Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria 3800, Australia.
Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria 3800, Australia.
Nat Commun. 2014 Jun 26;5:4239. doi: 10.1038/ncomms5239.
Bacterial autotransporters comprise a 12-stranded membrane-embedded β-barrel domain, which must be folded in a process that entraps segments of an N-terminal passenger domain. This first stage of autotransporter folding determines whether subsequent translocation can deliver the N-terminal domain to its functional form on the bacterial cell surface. Here, paired glycine-aromatic 'mortise and tenon' motifs are shown to join neighbouring β-strands in the C-terminal barrel domain, and mutations within these motifs slow the rate and extent of passenger domain translocation to the surface of bacterial cells. In line with this, biophysical studies of the autotransporter Pet show that the conserved residues significantly quicken completion of the folding reaction and promote stability of the autotransporter barrel domain. Comparative genomics demonstrate conservation of glycine-aromatic residue pairings through evolution as a previously unrecognized feature of all autotransporter proteins.
细菌自转运蛋白包含一个 12 股的膜嵌入β-桶状结构域，该结构域必须经过一个折叠过程，将 N 端的一个过客结构域片段包裹其中。自转运蛋白折叠的这个初始阶段决定了随后的易位是否能将 N 端结构域递送到细菌细胞表面的功能形式。在这里，相邻β-链之间的成对甘氨酸-芳香族“榫卯”结构域显示出相邻β-链之间的连接，而这些结构域中的突变会降低过客结构域易位到细菌细胞表面的速度和程度。与此一致的是，对自转运蛋白 Pet 的生物物理研究表明，保守残基显著加快了折叠反应的完成，并促进了自转运蛋白桶状结构域的稳定性。比较基因组学表明，甘氨酸-芳香族残基对的保守性是通过进化而来的，这是所有自转运蛋白的一个以前未被识别的特征。
