Letarov A V, Londer Y Y, Boudko S P, Mesyanzhinov V V
Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117871, Russia.
Biochemistry (Mosc). 1999 Jul;64(7):817-23.
Bacteriophage T4 fibritin is a triple-stranded, parallel, segmented alpha-helical coiled-coil protein. Earlier we showed that the C-terminal globular domain (foldon) of fibritin is essential for correct trimerization and folding of the protein. We constructed the chimerical fusion protein W31 in which the fibritin foldon sequence is followed by the small globular non-alpha-helical protein gp31 of the T4 phage. We showed that the foldon is capable of trimerization in the absence of the coiled-coil part of fibritin. A deletion mutant of fibritin (NB1) with completely deleted foldon is unable to fold and trimerize correctly. An excess of this mutant protein did not influence the refolding of fibritin in vitro, and the chimerical protein inhibited this process efficiently. Our conclusion is that the trimerization of the foldon is the initial step of fibritin refolding and is followed by the formation of the coiled-coil structure.
噬菌体T4纤维蛋白是一种三链、平行、分段的α-螺旋卷曲螺旋蛋白。我们之前表明，纤维蛋白的C端球状结构域（折叠子）对于该蛋白的正确三聚化和折叠至关重要。我们构建了嵌合融合蛋白W31，其中纤维蛋白折叠子序列之后是T4噬菌体的小球状非α-螺旋蛋白gp31。我们表明，在没有纤维蛋白卷曲螺旋部分的情况下，折叠子能够三聚化。完全缺失折叠子的纤维蛋白缺失突变体（NB1）无法正确折叠和三聚化。过量的这种突变蛋白在体外不影响纤维蛋白的重折叠，而嵌合蛋白则有效地抑制了这一过程。我们的结论是，折叠子的三聚化是纤维蛋白重折叠的起始步骤，随后是卷曲螺旋结构的形成。
