Lindberg I, Tu B, Muller L, Dickerson I M
Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, New Orleans 70112, USA.
DNA Cell Biol. 1998 Aug;17(8):727-34. doi: 10.1089/dna.1998.17.727.
The neuroendocrine protein 7B2 is a binding protein for the prohormone convertase 2 (PC2) and is required for the intracellular conversion of proPC2 to active PC2. Both full-length 7B2 and its carboxy-terminal 31-residue peptide (CT peptide) are capable of potent inhibition of PC2; the 7B2 protein thus regulates both the biosynthesis and the activity of PC2. Vertebrate 7B2s are highly conserved (92%-97% homology), and thus, species comparison has not been informative in assessing the crucial protein domains responsible for bioactivity. We here report the cloning of the Caenorhabditis elegans 7B2 protein. Although weakly conserved with the vertebrate sequences (23% similarity with mouse 7B2), C. elegans 7B2 contains the signature PPNPCP motif as well as a highly conserved heptapeptide within the CT peptide. In in vitro assays, C. elegans 7B2 possessed significant inhibitory activity against recombinant vertebrate PC2 (IC50 130 nM), and in two functional tests, the amino-terminal domain of C. elegans 7B2 facilitated the activation of proPC2. We conclude that despite low amino acid conservation overall, both functional domains within 7B2 have been conserved between the C. elegans and the vertebrate proteins.
神经内分泌蛋白7B2是激素原转化酶2（PC2）的结合蛋白，是激素原PC2在细胞内转化为活性PC2所必需的。全长7B2及其羧基末端31个残基的肽（CT肽）都能够有效抑制PC2；因此，7B2蛋白调节PC2的生物合成和活性。脊椎动物的7B2高度保守（同源性为92%-97%），因此，在评估负责生物活性的关键蛋白结构域时，物种比较并无参考价值。我们在此报告秀丽隐杆线虫7B2蛋白的克隆。尽管与脊椎动物序列的保守性较弱（与小鼠7B2的相似性为23%），但秀丽隐杆线虫7B2包含标志性的PPNPCP基序以及CT肽内一个高度保守的七肽。在体外试验中，秀丽隐杆线虫7B2对重组脊椎动物PC2具有显著的抑制活性（IC50为130 nM），并且在两项功能测试中，秀丽隐杆线虫7B2的氨基末端结构域促进了激素原PC2的激活。我们得出结论，尽管总体氨基酸保守性较低，但7B2内的两个功能结构域在秀丽隐杆线虫和脊椎动物蛋白之间是保守的。
