tailieunhanh - Báo cáo khoa học: Characterization of novel sequence motifs within N- and C-terminal extensions of p26, a small heat shock protein from Artemia franciscana

The small heat shock proteins function as molecular chaperones, an activ-ity often requiring reversible oligomerization and which protects against irreversible protein denaturation. An abundantly produced small heat shock protein termed p26 is thought to contribute to the remarkable stress resistance exhibited by encysted embryos of the crustacean,Artemia francis-cana. Three novel sequence motifs termed G, R and TS were individually deleted from p26 by site-directed mutagenesis. | iFEBS Journal Characterization of novel sequence motifs within N- and C-terminal extensions of p26 a small heat shock protein from Artemia franciscana Yu Sun and Thomas H. MacRae Department of Biology Dalhousie University Halifax Canada Keywords molecular chaperone p26 structure function small heat shock protein stress resistance Artemia franciscana Correspondence T. H. MacRae Department of Biology Dalhousie University Halifax . B3H 4J1 Canada Fax 1 902 494 3736 Tel 1 902 494 6525 E-mail tmacrae@ Received 9 June 2005 revised 11 August 2005 accepted 16 August 2005 doi The small heat shock proteins function as molecular chaperones an activity often requiring reversible oligomerization and which protects against irreversible protein denaturation. An abundantly produced small heat shock protein termed p26 is thought to contribute to the remarkable stress resistance exhibited by encysted embryos of the crustacean Artemia francis-cana. Three novel sequence motifs termed G R and TS were individually deleted from p26 by site-directed mutagenesis. G encompasses residues G8-G29 a glycine-enriched region and R includes residues R36-R45 an arginine-enhanced sequence both in the amino terminus. TS composed of residues T169-T186 resides in the carboxy-extension and is augmented in threonine and serine. Deletion of R had more influence than removal of G on p26 oligomerization and chaperoning the latter determined by thermotolerance induction in Escherichia coli protection of insulin and citrate synthase from dithiothreitol- and heat-induced aggregation respectively and preservation of citrate synthase activity upon heating. Oligomerization of the TS and R variants was similar but the TS deletion was slightly more effective than R as a chaperone. The extent of p26 structural perturbation introduced by internal deletions including modification of intrinsic fluorescence 1-anilino-8-naphthalene-sulphonate binding and secondary structure .