Electron transfer complexes of cytochrome c peroxidase from Paracoccus denitrificans containing more than one cytochrome

Paracoccus denitrificans can accommodate horse cytochrome c and Paracoccus cytochrome c550 at different sites on its molecular surface. Here we use 1H NMR spectroscopy, analytical ultracentrifugation, molecular docking simulation, and microcalorimetry to investigate whether these small cytochromes can be accommodated simultaneously in the formation of a ternary complex. The pattern of perturbation of heme methyl and methionine methyl resonances in binary and ternary solutions shows that a ternary complex can be formed, and this is confirmed by the increase in the sedimentation coefficient upon addition of horse cytochrome c to a solution in which cytochrome c550 fully occupies its binding site on cytochrome c peroxidase. Docking experiments in which favored binary solutions of cytochrome c550 bound to cytochrome c peroxidase act as targets for horse cytochrome c and the reciprocal experiments in which favored binary solutions of horse cytochrome c bound to cytochrome c peroxidase act as targets for cytochrome c550 show that the enzyme can accommodate both cytochromes at the same time on adjacen

Sexual Risk, Serostatus and Intimate Partner Violence Among Couples During Pregnancy in Rural South Africa

The aim of this study was to describe sexual risk behavior among 239 couples during pregnancy and to examine the relationship of sexual risk behavior with HIV serostatus and intimate partner violence. One-third (31.8 %) of pregnant women and 20.9 % of male partners were HIV positive. HIV risk factors included lack of knowledge of partners’ HIV serostatus, unprotected sexual intercourse and multiple sexual partners. Among men, multivariate logistic regression identified awareness of HIV negative partner status, multiple sexual partners and low levels of partner violence and among women Zulu or Swati ethnicity were associated with unprotected intercourse. HIV positive concordance was associated with protected sex and in multilevel analysis of couples HIV positive status and awareness of the partner’s HIV positive status were associated with protected sex. High levels of HIV risk behaviour was found among couples during pregnancy calling for HIV risk reduction interventions