Tadokoro Akiko, Hayashi Hidemi, Kishimoto Toshihiko, Makino Yasutaka, Fujisaki Shingo, Nishimura Yukinobu
Department of Biomolecular Sciences, Faculty of Science, Toho University, Miyama 2-2-1, Funabashi, Chiba, 274-8510.
J Biochem. 2004 Feb;135(2):185-91. doi: 10.1093/jb/mvh022.
Escherichia coli spr (suppressor of prc) mutants and nlpI mutants show thermosensitive growth. The thermosensitivity of the spr mutants was suppressed by the nlpI mutations. Expression of the fusion genes encoding hexa-histidine-tagged NlpI (NlpI-His) and purification of the tagged NlpI showed that NlpI-His bound with Prc protease and IbpB chaperone. NlpI-His with the amino acid substitution of G103D did not bind with either of these proteins, while NlpI-His variants (NlpI-284-His, NlpI-Q283-His, and NlpI-G282-His) lacking 10 to 12 residues from the carboxy terminus bound with both proteins. The tagged NlpI lacking 11 amino acid residues from the carboxy terminus was processed by Prc, but that lacking 12 residues was not. The thermosensitivity of the nlpI mutant was corrected by the production of the former NlpI variant, but not by production of the latter. Expression of the truncated NlpI that lacked 10 or 11 residues from the carboxy terminus corrected the thermosensitivity of the prc nlpI double mutant, while expression of the full-length NlpI did not. Thus, it was suggested that NlpI was activated by Prc protease processing.
大肠杆菌spr（prc抑制因子）突变体和nlpI突变体表现出温度敏感型生长。spr突变体的温度敏感性被nlpI突变所抑制。编码六组氨酸标签化NlpI（NlpI-His）的融合基因的表达以及标签化NlpI的纯化表明，NlpI-His与Prc蛋白酶和IbpB伴侣蛋白结合。G103D氨基酸取代的NlpI-His不与这两种蛋白质中的任何一种结合，而从羧基末端缺失10至12个残基的NlpI-His变体（NlpI-284-His、NlpI-Q283-His和NlpI-G282-His）与这两种蛋白质都结合。从羧基末端缺失11个氨基酸残基的标签化NlpI被Prc加工，但缺失12个残基的则未被加工。nlpI突变体的温度敏感性通过产生前一种NlpI变体得到校正，但后一种则不能。从羧基末端缺失10或11个残基的截短型NlpI的表达校正了prc nlpI双突变体的温度敏感性，而全长NlpI的表达则不能。因此，提示NlpI通过Prc蛋白酶加工而被激活。
