Hall T M, Porter J A, Young K E, Koonin E V, Beachy P A, Leahy D J
Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Cell. 1997 Oct 3;91(1):85-97. doi: 10.1016/s0092-8674(01)80011-8.
The approximately 25 kDa carboxy-terminal domain of Drosophila Hedgehog protein (Hh-C) possesses an autoprocessing activity that results in an intramolecular cleavage of full-length Hedgehog protein and covalent attachment of a cholesterol moiety to the newly generated amino-terminal fragment. We have identified a 17 kDa fragment of Hh-C (Hh-C17) active in the initiation of autoprocessing and report here its crystal structure. The Hh-C17 structure comprises two homologous subdomains that appear to have arisen from tandem duplication of a primordial gene. Residues in the Hh-C17 active site have been identified, and their role in Hedgehog autoprocessing probed by site-directed mutagenesis. Aspects of sequence, structure, and reaction mechanism are conserved between Hh-C17 and the self-splicing regions of inteins, permitting reconstruction of a plausible evolutionary history of Hh-C and the inteins.
果蝇刺猬蛋白（Hh-C）约25 kDa的羧基末端结构域具有自加工活性，可导致全长刺猬蛋白的分子内切割，并使胆固醇部分共价连接到新生成的氨基末端片段上。我们鉴定出了Hh-C的一个17 kDa片段（Hh-C17），它在自加工起始过程中具有活性，并在此报告其晶体结构。Hh-C17结构由两个同源亚结构域组成，这两个亚结构域似乎源于一个原始基因的串联复制。已确定了Hh-C17活性位点中的残基，并通过定点诱变研究了它们在刺猬蛋白自加工中的作用。Hh-C17与内含肽的自我剪接区域在序列、结构和反应机制方面存在保守性，这使得我们能够重建Hh-C和内含肽合理的进化史。
