Jia Z, Quail J W, Delbaere L T, Waygood E B
Department of Chemistry, University of Saskatchewan, Saskatoon, Canada.
Biochem Cell Biol. 1994 May-Jun;72(5-6):202-17. doi: 10.1139/o94-030.
The phosphocarrier protein HPr is a central component of the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) that is responsible for carbohydrate uptake in many bacterial species. A number of three-dimensional structures of HPrs from both Gram-positive and Gram-negative bacteria have been determined; the overall folding topology of HPr is an open-faced beta-sandwich composed of three alpha-helices and a beta-sheet. A detailed structural comparison of these HPrs has been carried out. Besides the overall main chain folding, many detailed structural features are well conserved in all HPr structures. The three x-ray structures of HPrs from Escherichia coli, Streptococcus faecalis, and Bacillus subtilis show considerable overall similarity with respect to the positions of the C alpha atoms. A significant structural difference between HPrs from Gram-positive and Gram-negative bacteria is found in the region of Gly54, owing to the steric effects of Tyr37 in HPrs from the Gram-positive species. The region around Gly54 is involved in the binding of HPr to other PTS proteins and the differences in this region may be responsible for some of the poor functional complementation between HPrs from Gram-positive and Gram-negative species. The active center region, residues 12-18, appears to have significant differences in the comparisons between the overall structures. These differences support the proposal that phosphorylation and dephosphorylation of the active site His15 is accompanied by conformational changes. However, a local structural comparison of residues 12-18 from the x-ray structures of HPrs from E. coli and B. subtilis, and the two-dimensional nuclear magnetic resonance structure of B. subtilis HPr suggests that there is a conserved active center involving residues His15, Arg 17, and Pro18, which shows little conformational change during the phosphorylation cycle. The results of other experimental approaches, including site-directed mutagenesis and NMR spectroscopy, are in some cases difficult to rationalize with some of the details of the structures, but do appear to favour the conclusion that little conformational change occurs.
磷酸载体蛋白HPr是细菌磷酸烯醇丙酮酸：糖磷酸转移酶系统（PTS）的核心组成部分，该系统负责许多细菌种类中碳水化合物的摄取。已经确定了来自革兰氏阳性菌和革兰氏阴性菌的多种HPr的三维结构；HPr的整体折叠拓扑结构是一个由三个α螺旋和一个β折叠组成的开放式β三明治结构。已经对这些HPr进行了详细的结构比较。除了整体主链折叠外，许多详细的结构特征在所有HPr结构中都保存得很好。来自大肠杆菌、粪肠球菌和枯草芽孢杆菌的HPr的三种X射线结构在Cα原子位置上显示出相当大的整体相似性。由于革兰氏阳性菌来源的HPr中Tyr37的空间效应，在Gly54区域发现革兰氏阳性菌和革兰氏阴性菌来源的HPr之间存在显著的结构差异。Gly54周围的区域参与HPr与其他PTS蛋白的结合，该区域的差异可能是革兰氏阳性菌和革兰氏阴性菌来源的HPr之间功能互补性较差的部分原因。活性中心区域，即第12 - 18位残基，在整体结构比较中似乎存在显著差异。这些差异支持了活性位点His15的磷酸化和去磷酸化伴随着构象变化的观点。然而，对来自大肠杆菌和枯草芽孢杆菌的HPr的X射线结构中第12 - 18位残基以及枯草芽孢杆菌HPr的二维核磁共振结构进行局部结构比较表明，存在一个保守的活性中心，涉及His15、Arg 17和Pro18残基，在磷酸化循环过程中其构象变化很小。其他实验方法的结果，包括定点诱变和核磁共振光谱法，在某些情况下难以与结构的一些细节相协调，但似乎确实支持构象变化很小这一结论。
