Beta2-strand of salivary S cystatins: a "chemeleon sequence".

Alberto Vitali, Cristiana Carelli Alinovi, Maria Cristina De Rosa, Raffaele Petruzzelli

Istituto di Biochimica e Biochimica Clinica, Facoltà di Medicina, Università Cattolica e/o Istituto per la Chimica del Riconoscimento Molecolare, C.N.R., Largo F. Vito 1, Rome, Italy.

Biochemical and biophysical research communications 2009 Sep 11

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Secondary structure prediction of salivary cystatins S, SA, and SN carried out by several methods label the 39-58 sequence (beta2-strand) as predominantly alpha-helical. The helical propensity of a peptide corresponding to beta2-strand of salivary SA cystatin analyzed by CD display high helical propensity in aqueous solution, whereas peptides matching the beta2-strand amino acid sequence of cystatins S and SN, display random coil conformation in aqueous solution but acquire alpha-helical conformation in the presence of trifluoroethanol (TFE). Moreover molecular dynamics simulation performed on the homology modeling of cystatin SA constructed on 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 beta2-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.

Citation

Alberto Vitali, Cristiana Carelli Alinovi, Maria Cristina De Rosa, Raffaele Petruzzelli. Beta2-strand of salivary S cystatins: a "chemeleon sequence". Biochemical and biophysical research communications. 2009 Sep 11;387(1):47-51