Synthesis, characterization, and conformational analysis of the D/L-Tic7 stereoisomers of the bradykinin receptor antagonist D-Arg0[Hyp3,Thi5,D-Tic7,Oic8]bradykinin

D-Arg0[Hyp3,Thi5,D-Tic7,Oic8]bradykinin (HOE-140) is a potent (Ki = 0.11 nM) inhibitor of [3H]bradykinin binding to bradykinin B2 receptors found on human IMR-90 fetal lung fibroblasts. During the synthesis of this compound, we isolated and unambiguously identified the L-Tic7 stereoisomer (WIN 65365), which exhibits a 2000-fold lower binding affinity (Ki = 130 nM) than HOE-140 to the bradykinin receptor. A similar decrease in potency is observed for WIN 65365 inhibition of bradykinin-stimulated 45Ca2+ efflux from IMR-90 cells. Both HOE-140 and WIN 65365 appear to be competitive antagonists at the IMR-90 bradykinin receptor. This is the first documentation of bradykinin binding and functional antagonist activity by a bradykinin peptide analogue with an L amino acid replacing Pro7. In an attempt to rationalize the differences in binding affinities of HOE-140 and WIN 65365, a conformational analysis of the peptides was undertaken using annealed molecular dynamics (AMD). Conformational analysis of HOE-140 reveals a strong preference for the formation of a type II' beta-turn in the carboxy-terminal region. Analogous modeling of WIN 65365 reveals that its conformation is strikingly different from HOE-140 in that the four carboxy-terminal residues of WIN 65365 do not form a beta-turn. These differences in low-energy conformations between the two peptides may lead to a better understanding of the molecular interaction of antagonists with the bradykinin receptor.

Structure determination, pharmacological evaluation, and structure-activity studies of a new cyclic peptide substance P antagonist containing the new amino acid 3-prenyl-beta-hydroxytyrosine, isolated from Aspergillus flavipes

Two novel cyclic heptapeptides, peptides 1a and 1c, were isolated from an Aspergillus flavipes culture, originally isolated from soil, and their structures established by chemical and spectroscopic evidence. Peptide 1a contains a new amino acid, 3-prenyl-beta-hydroxytyrosine, and is a competitive antagonist to substance P at the human NK1 receptor, with an inhibitor affinity constant (Ki) of 8 +/- 4 microM. Methylation of 1a gave the monomethyl derivative 1b, which is a more potent competitive antagonist, with a Ki of 0.12 +/- 0.03 microM at the human NK1 receptor. Herein we report the structure determinations of 1a and 1c, and some structure-activity results. Several analogs of 1a were prepared by derivatization and synthesis. Structure-activity results for these analogs confirmed that the 3-prenyl-beta-hydroxytyrosine moiety is critical for the biological potency of 1a and 1b.

Primary structure of a 7Fe ferredoxin from Streptomyces griseus

The complete primary structure of a Streptomyces griseus (ATCC 13273) 7Fe ferredoxin, which can couple electron transfer between spinach ferredoxin reductase and S. griseus cytochrome P-450soy for NADPH-dependent substrate oxidation, has been determined by Edman degradation of the whole protein and peptides derived by Staphylococcus aureus V8 proteinase and trypsin digestion. The protein consists of 105 amino acids and has a calculated molecular weight, including seven irons and eight sulfurs, of 12,291. The ferredoxin sequence is highly homologous (73%) to that of the 7Fe ferredoxin from Mycobacterium smegmatis. The N-terminal half of the sequence, which is the Fe-S clusters binding domain, has more than 50% homology with other 7Fe ferredoxins. In particular, the seven cysteines known from the crystal structure of Azotobacter vinelandii ferredoxin I to be involved in binding the two Fe-S clusters are conserved.

Classification of malnutrition by statistical analysis of quantitative two-dimensional gel electrophoresis of plasma proteins

An attempt to use the relative concentrations of major plasma proteins for clinical assessment of severe malnutrition is described. Quantitative two-dimensional gel electrophoresis was used to measure the concentrations of 24 major proteins in small aliquots of plasma obtained from children, aged 0 to 3 years, who were patients and outpatients in Liberian hospitals. Fifteen had a clinical diagnosis of kwashiorkor, 36 were diagnosed with marasmus, and 18 were controls. There were also 5 controls from the United States. The individuals were placed in six groups; kwashiorkor, kwashiorkor who died during treatment, marasmus, marasmus who died, Liberian controls, and U.S. controls. The amount of protein in each spot in the two-dimensional gels was estimated by measuring bound stain using a laser scanner and computerized image analysis. We found very low serum transferrin levels in malnourishment, in agreement with reports from other investigators. All of the data for 24 protein variables were pooled for factor analysis; the mean factor scores for each group differed, with the kwashiorkor groups furthest from the controls. Results of discriminant analysis using the amounts of different numbers of protein variables (3 to 24) were compared for posterior assignment of individuals to groups. The validity of the method was tested by analysis of plasma aliquots obtained from patients following initiation of therapy and which were not a part of the training set. Predictive performance (prognosis of patient survival) depended upon the number of protein variables used. Although artifactual fitting of the data is expected to contribute to performance as the number of variables is increased, use of as many as 7 variables may be justified, even with our small patient groups. Possible use of these results for development of a practical clinical test is discussed.