ISSN:
1573-4943
Keywords:
CD
;
disulfide bond
;
protein stability
;
RIA
;
secondary structure
;
tyrosine ionization
;
xylanase
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The role of a S-S cross-link in the conformational stability of xylanase fromHumicola lanuginosa has been investigated using CD, UV absorption spectroscopy, and RIA displacement studies. Our studies show that reduction and carboxymethylation of the S-S cross-link in xylanase results in a gross conformational perturbation of the protein. The secondary structure analysis of the CD spectra indicates that the xylanase with an intact S-S contains 66% β-sheet structure and remaining random coil. Cleavage of the S-S bond results in a loss of 25% β-sheet structure. Thermal denaturation studies using CD spectroscopy andpH-dependent tyrosine ionization studies using UV spectroscopy show that the presence of disulfide cross-link offers resistance against unfolding by extremes of temperature andpH. Further, we demonstrate that the heat-induced changes in xylanase with intact S-S bond are almost totally reversible, while those in the S-S cleaved enzyme fail to show any significant reversal. Our studies support the present theory that S-S cross-links exert their stabilizing effect in proteins by destabilizing the unfolded state of the protein and forcing it back to a more folded state.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01025018
Permalink