Biochemical and Biophysical Research Communications, Vol.387, No.1, 47-51, 2009
beta 2-Strand of salivary S cystatins: A "chemeleon sequence"
Secondary structure prediction of salivary cystatins S, SA, and SN carried Out by several methods label the 39-58 sequence (beta 2-strand) as predominantly alpha-helical. The helical propensity of a peptide corresponding to beta 2-strand of salivary SA cystatin analyzed by CD display high helical propensity in aqueous solution, whereas peptides matching the beta 2-strand amino acid sequence of cystatins S and SN, display random coil conformation in aqueous solution but acqurie alpha-helical conformation in the presence of trifluoroethanol (TFE). Moreover molecular dynamics simulation performed oil the homology modeling of cystatin SA constructed oil the basis of recently determined three-dimensional structure of salivary cystatin D, Suggests that cystatin SA does not significantly deviate from the starting structure over the course of the simulation. The results obtained indicate that the beta 2-strand of salivary S cystatins has high helical propensity when isolated from native protein and acquire the final beta structure by interaction with the rest of the polypeptide chain. (C) 2009 Elsevier Inc. All rights reserved.
Keywords:Salivary cystatins;beta-Strand;alpha-Heiix;CD;Molecular modeling;Folding;Peptide;Capping box