|Antoine, Wesner - UNIVERSITY OF MISSOURI|
Submitted to: Annual Missouri Symposium
Publication Type: Abstract Only
Publication Acceptance Date: April 22, 2005
Publication Date: April 22, 2005
Citation: Antoine, W., Miernyk, J.A. 2005. The osslt1 protein has both chaperone and protease activities [abstract]. Twenty-Second Annual Missouri Symposium. p. 137. Technical Abstract: The AtSLT1 and NtSLT1 proteins were able to complement a calcineurin-deficient mutant of Saccharomyces cerevisiae (CNB1) that has a salt-sensitive phenotype. Little is known about the biochemical basis of this complementation. Using the InterProScan program, we were able to identify two major signature domains in the SLT1 protein sequence; a peptidase M14 domain near the N-terminus, and a Hsp20 chaperone-like domain close to the C-terminus. We have cloned the full-length cDNA of the rice (Oryza sativa) homolog (OsSLT1), and expressed the full-length, N-terminal truncated (delta 1-217), and C-terminal truncated (delta 446-521) forms of the protein in Escherichia coli. The recombinant proteins were analyzed in vitro. The OsSLT1 protein prevented heat-induced aggregation of citrate synthase as well as DTT-induced aggregation of lysozyme. The C-terminal acidic domain partially inhibited chaperone activity of the full-length protein. The OsSLT1 protein was able to degrade casein as observed by SDS-PAGE and detected using fluorescein-labeled casein. The OsSLT1 protein was also able to hydrolize ATP. Calcineurin is a type 2B protein phosphatase, and the common property of phosphate-ester hydrolysis links calcineurin and the plant STL1 proteins. These observations might explain how OsSLT1 was able to complement the yeast CNB1 mutant; both proteins might dephosphorylating a common molecule downstream in a pathway leading to ion homeostasis and salt tolerance.