Biomedical subjects
Publications and source records attributed to W G Kruggel.
Multiple myotoxin a sequences have been determined from the venom of a single adult male prairie rattlesnake (Crotalus viridis viridis). This is the first time such individual variation has been reported for this toxin class and the number of isoforms suggest that myotoxin a is the product of a duplicated locus.
The complete sequence of the basis subunit of Mojave toxin from the venom of the Mojave rattlesnake (Crotalus s. scutulatus) is presented. It is shown to have great similarity to the basic subunits of related toxins from the venoms of the South American and midget faded rattlesnakes.
The chemical nature of the inactivation of citrate synthase by S-(4-bromo-2,3-dioxobutyl)-CoA, an active site-directed irreversible inhibitor, has been investigated. Active site-directed inactivation leads to derivatization of either Lys22 by epsilon-amino Schiff base formation or Glu363 by apparent alkylation of the gamma-carboxyl group, respectively. Lys22 is labeled in the tight (catalytic) form of the enzyme while Glu363 is labeled in the open (product release) form. Glu363 and Lys22 are both located at or near the entrance to an active site in the crystal structure of citrate synthase (Remington, S., Wiegand, G., and Huber, R. (1982) J. Mol. Biol. 158, 111-152). Glu363 is in the sequence of the protomer forming the active site while Lys22 is in the sequence of the other polypeptide in the homodimer. Labeling in this region appears to inactivate the enzyme by preventing access of substrates to the active site. A distinct and separate labeling process involves derivatization of Asn192 in the tight (catalytic) form and Ser198 and/or Ser199 in the open (product release) form at a locus far removed from the active site. Labeling at the second site may simply identify chemically reactive residues, or it may identify the binding site for long chain acyl-CoA, which has been identified as a possible allosteric negative effector of citrate synthase (Caggiano, A. V., and Powell, G. L. (1979) J. Biol. Chem. 254, 2800-2806). This second labeling process apparently inactivates the enzyme by interfering with catalytically essential conformational changes.
The complete amino acid sequence of the basic subunit of crotoxin from the venom of Crotalus durissus terrificus has been determined. Fragmentation of the protein was achieved by using cyanogen bromide and arginine- and lysine-specific endoproteases. Sixteen Glx and Asx residues reported by Fraenkel-Conrat et al. (1980) in Natural Toxins (D. Eaker and T. Wadstrom, eds.), pp. 561-567, Pergamon, Oxford.) have been resolved as Glu or Gln and Asp or Asn residues, respectively. Most of the remaining sequence is identical to that reported by the foregoing authors although several significant differences were evident in our protein. Tyr-61 was not present; thus the correct sequence is Lys-60, Trp-61. The latter sequence aligns with sequences of all other known viperid and crotalid phospholipases A2 (S. D. Aird, I. I. Kaiser, R. V. Lewis, and W. G. Kruggel (1985) Biochemistry 24, 7054-7058). Other differences include Asx-99, which is Ser, and Asx-105, which is Tyr. Some positions display allelic variation. In some lots of venom Glx-33 is Gln, while in others it is Arg. Positions 37 and 69 occur as mixtures of both Lys and Arg. Amino acid sequence comparisons between the basic and acidic subunits of crotoxin and between the basic subunit and other phospholipase A2 molecules indicate that the basic subunit is structurally most similar to the monomers of nontoxic, dimeric phospholipases A2 from the venoms of Crotalus adamanteus, Crotalus atrox, and Trimeresurus okinavensis, and to the toxic monomeric phospholipase A2 from the venom of Bitis caudalis.
Crotoxin and homologous crotalid presynaptic neurotoxins consist of a toxic, basic subunit and a slightly smaller, nontoxic, acidic subunit. The latter, in turn, consists of three chains, interconnected by disulfide bonds. The complete sequences of two of the three acidic subunit chains of crotoxin, from the venom of the South American rattlesnake Crotalus durissus terrificus, have been determined. In addition, all but the ten amino-terminal residues of the third chain have been sequenced. Sequence comparison data suggest that the acidic subunit has been derived from a nontoxic, homodimeric, crotalid phospholipase A2. When compared with sequences of phospholipases A2, the acidic subunit lacks a 22-residue amino-terminal segment and two additional segments that are implicated in phospholipid substrate binding. However, it apparently retains an intact active site, the calcium binding loop, and segments involved in subunit binding in homodimeric phospholipases A2. The C chain of the acidic subunit shows strong homology with mammalian neurophysins, lending possible support to the hypothesis that the acidic subunit functions as a chaperone to prevent nonspecific binding of the toxic basic subunit. Crystals suitable for X-ray diffraction studies have recently been produced [Achari, A., Radvanyi, F. R., Scott, D., Bon, C., & Sigler, P. B. (1985) J. Biol. Chem. 260, 9385-9387]; thus with these data it should now be possible to determine the three-dimensional structure of the intact neurotoxin and dissociated subunits.
Explore the source record for details and available documents.
Near-infrared spectral absorption properties were determined for emulsified and ground meat samples. Six corrected log numbers associated with the optical responses of 6 filters in the InfraAlyzer were used as multiple independent variables in regression equations. Dependent variables for the equations were moisture, determined by oven-drying; fat, determined by Goldfisch extraction; and protein, determined by the Kjeldahl method. InfraAlyzer log values, replicated 4 times on each emulsified beef sample and 3 times on each ground lamb sample, increased as the samples were warmed from the heat generated in the sample drawer. Variation in temperature of the meat samples were partially responsible for differences in constant terms and in regression coefficients for equations developed on data from different replications of a sample. Multiple correlation coefficients for fat ranged from 0.91 to 0.94 in emulsified meat and from 0.83 to 0.85 in ground meat; for moisture, 0.90-0.94 and 0.83-0.85, respectively; and for protein, 0.80-0.85 and 0.72-0.77, respectively. Overall, near-infrared reflectance shows promise as a rapid method for determining composition of meat. Nevertheless, some aspects of near-infrared reflectance require further attention.
Explore the source record for details and available documents.
Explore the source record for details and available documents.