“
“One of the steps of a common pathway for biological energy conversion involves electron transfer between cytochrome c and cytochrome

bc(1). To clarify the mechanism of this reaction, we examined the structural association of those two proteins using the electron transfer-independent electron paramagnetic resonance (EPR) techniques. Drawing on the differences in the continuous wave EPR check details spectra and saturation recoveries of spin-labeled bacterial and mitochondrial cytochromes c recorded in the absence and presence of bacterial cytochrome bc(1), we have exposed a time scale of dynamic equilibrium between the bound and the free state of cytochrome c at various ionic strengths. Our data show a successive decrease of the bound cytochrome c fraction as the ionic strength increases, with a limit of similar to 120 mM NaCl buy P005091 above which essentially no bound cytochrome c can be detected by EPR. This limit does not apply to all of the interactions of cytochrome c with cytochrome

bc(1) because the cytochrome bc(1) enzymatic activity remained high over a much wider range of ionic strengths. We concluded that EPR monitors just the tightly bound state of the association and that an averaged lifetime of this state decreases from over 100 mu s at low ionic strength to less than 400 ns at an ionic strength above 120 mM. This suggests that at physiological ionic selleck chemicals strength, the tightly bound complex on average lasts less than the time needed for a single electron exchange between hemes c and c(1), indicating that productive electron transfer requires several collisions of the two molecules. This is consistent

with an early idea of diffusion-coupled reactions that link the soluble electron carriers with the membranous complexes, which, we believe, provides a robust means of regulating electron flow through these complexes.”
“Objective: There are many genes reported to have been associated with combined pituitary hormone deficiencies, but mutations in HESX1 strongly correlate with septo-optic dysplasia. Our aim was to determine the cause of panhypopituitarism in our patient.\n\nPatients and methods: We studied an 8-month-old child having panhypopituitarism. The coding exons of PIT1, PROP1, LHX3, and HESX1 genes were amplified. Direct sequencing was done after denaturing HLPC.\n\nResults: We identified a novel homozygous mutation (R160H) within the homeodomain of HESX1, which, to our knowledge, is the first to be described in humans. Neuroimaging studies revealed anterior pituitary aplasia, a normal posterior pituitary gland, and a thin pituitary stalk but no midline abnormalities. Optic nerve studies showed no pathology. This mutation is also carried in the parents of the affected child in a heterozygous pattern, suggesting an autosomal recessive inheritance.