Biomaterial Database

beta Structure of aqueous staphylococcal enterotoxin B by spectropolarimetry and sequence-based conformational predictions. 1976

P A Muñoz, and J R Warren, and M E Noelken

Conformations of the globular protein staphylococcal enterotoxin B have been examined experimentally by ultraviolet circular dichroism (CD) and visible optical rotatory dispersion (ORD). Chen-Yang-Chau analysis (Chen, Y.-H., Yang, J.T., and Chau, K. H. (1974), Biochemistry 13, 3350) of the far-ultraviolet CD spectrum of native enterotoxin B revealed (assuming an average helix length of 11 residues) 9% alpha helix, 38% beta structure, and 53% random coil. A fourfold increase in alpha-helix was observed for enterotoxin exposed to 0.2% sodium dodecyl sulfate, behavior typical for globular proteins of low helical content. Values of -40 to -50 for the Moffitt-Yang parameter b0 calculated from visible ORD suggested 6-13% alpha helix in native enterotoxin. Application of a new predictive model (Chou, P. Y., and Fasman, G. D. (1974), Biochemistry 13,222) to the amino acid sequence of enterotoxin B indicated 11% alpha helix, 34% beta structure, and 55% coil in native enterotoxin. The excellent agreement for the amount of alpha and beta conformation utilizing different optical and predictive methods indicates beta structure as the dominant secondary structure in native enterotoxin B. Most of the beta structure is predicted by Chou-Fasman analysis to reside in two large regions of antiparallel beta sheet involving residues 81-148 and residues 184-217. Such highly cooperative regions of anti-parallel beta sheet account for the slow unfolding of enterotoxin B in concentrated guanidine hydrochloride and rapid folding of guanidine hydrochloride denatured enterotoxin B to native conformation(s) (Warren, J.R., Spero, L., and Metzger, J. F. (1974), Biochemistry 13, 1678). A more than twofold increase in alpha-helix content with a small diminution in beta structure was detected by CD and ORD upon acidification of aqueous enterotoxin to pH 2.5. Thus, the beta structure of enterotoxin B appears to resist isothermal denaturation and constitutes a stable interior core of structure in the enterotoxin molecule.

UI	MeSH Term	Description	Entries
D009905	Optical Rotatory Dispersion	The method of measuring the dispersion of an optically active molecule to determine the relative magnitude of right- or left-handed components and sometimes structural features of the molecule.	Dispersion, Optical Rotatory,Rotatory Dispersion, Optical
D011336	Probability	The study of chance processes or the relative frequency characterizing a chance process.	Probabilities
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D002942	Circular Dichroism	A change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Circular Dichroism, Vibrational,Dichroism, Circular,Vibrational Circular Dichroism
D004768	Enterotoxins	Substances that are toxic to the intestinal tract causing vomiting, diarrhea, etc.; most common enterotoxins are produced by bacteria.	Staphylococcal Enterotoxin,Enterotoxin,Staphylococcal Enterotoxins,Enterotoxin, Staphylococcal,Enterotoxins, Staphylococcal
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000596	Amino Acids	Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.	Amino Acid,Acid, Amino,Acids, Amino
D013056	Spectrophotometry, Ultraviolet	Determination of the spectra of ultraviolet absorption by specific molecules in gases or liquids, for example Cl2, SO2, NO2, CS2, ozone, mercury vapor, and various unsaturated compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Ultraviolet Spectrophotometry
D013210	Staphylococcus	A genus of gram-positive, facultatively anaerobic, coccoid bacteria. Its organisms occur singly, in pairs, and in tetrads and characteristically divide in more than one plane to form irregular clusters. Natural populations of Staphylococcus are found on the skin and mucous membranes of warm-blooded animals. Some species are opportunistic pathogens of humans and animals.