Conformation of the neurotoxin crotoxin complex and its subunits

Journal Article · Tue May 01 04:00:00 EDT 1979 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00576a008· OSTI ID:5761724

Hanley, M R

Crotoxin, the neurotoxin from Crotalus durissus terrificus venom, and its two subunits, crotoxin A and crotoxin B, have been examined by fluorescence and circular dichroism techniques. Model spectra of crotoxin, generated from the expected contributions of the individual subunits, agreed with experimental results only at pH 2, where crotoxin was fully dissociated. From pH 4 to 10, crotoxin spectra could not be simulated by subunit contributions. Comparison of the results at pH values favoring either association or dissociation indicated that complex formation was accompanied by: (1) a 70% decrease in fluorescent emission intensity and a 7-nm blue shift of the emission maximum, (2) an increase in the far-ultraviolet circular dichroism, and (3) a marked intensity enhancement of the near-ultraviolet circular dichroism spectrum. These observations were taken as evidence that tryptophan residues were masked by complex formation and that the crotoxin complex contained an increased proportion of ordered secondary structure, particularly ..beta.. sheets. The results did not distinguish between conformational changes with subunit interaction or creation of ordered structure only at the subunit binding interface. Structural flexibility of the subunits was suggested from their ability to undergo reversible state changes by exposure to acid pH or guanidine hydrochloride. Examination of the concentration dependence of guanidine hydrochloride denaturation indicated that complex formation gave increased stability, although the subunits were individually quite resistant to guanidine hydrochloride denaturation. It is concluded that the ability of crotoxin and its subunits to exist in several reversible states is related to the control of the association-dissociation equilibrium of the complex and that conformational interconversion may be necessary for crotoxin to act on different target membranes.

• Research Organization: Univ. of California, Berkeley
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5761724
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 18:9; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
ANTIGENS
AZOLES
CARBONIC ACID DERIVATIVES
CARBOXYLIC ACIDS
COMPLEXES
CONFORMAL GROUPS
DICHROISM
EMISSION SPECTROSCOPY
FLUORESCENCE SPECTROSCOPY
GUANIDINES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INDOLES
LIE GROUPS
OPTICAL PROPERTIES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHYSICAL PROPERTIES
PYRROLES
SPECTRA
SPECTROSCOPY
STRUCTURAL CHEMICAL ANALYSIS
SYMMETRY GROUPS
TOXIC MATERIALS
TOXINS
TRYPTOPHAN
ULTRAVIOLET SPECTRA
VENOMS