Molecular characterization of a calponin-like protein from Schistosoma japonicum

The gene for a Schistosoma japonicum (Philippine strain origin) (Sjp) calpo nin-like protein has been cloned and characterised. The clone, designated P 14, was isolated from a Sjp adult worm lambda ZAP cDNA library by immunoscr eening, and was shown to contain a full-length cDNA encoding a 38.3 kDa pro tein that shared significant sequence similarity to a number of previously reported calponins and 22 kDa smooth-muscle proteins. Northern analysis ind icated the P14 transcript was approximate to 2.2 kb in both Sjp and Chinese strain S. japonicum (Sjc) adult worms. Southern blot analysis of genomic D NA suggested that several copies of the P14 gene are present in the Sjc and Sjp genomes but only one copy was evident in the S. mansoni (Sm) genome. W estern blot analysis indicated that the product of P14 occurs as a 38 kDa p rotein in adult Sjp worms and homologues are present in adult worms of Sjc and Sm. At least six isoforms, all with a similar molecular size of approxi mate to 38 kDa and isoelectric points ranging from 8.1 to 9.5, were present in adult Sjc worms. The protein was immunolocalized to the muscle of male and female Sjc adult worms. Recombinant protein was expressed in E. coli an d purified under denaturing conditions, and in yeast to produce a soluble p rotein in purified form. The availability of purified, correctly folded pro tein will allow investigations into its biological functions and potential involvement in host immunity. (C) 1999 Published by Elsevier Science B.V. A ll rights reserved.