The beta-subunit of the bovine mitochondrial F1 ATPase specifically binds the amino terminal domain of parathyroid hormone

Vaginal metabolome: towards a minimally invasive diagnosis of microbial invasion of the amniotic cavity in women with preterm labor

Microbial invasion of the amniotic cavity (MIAC) is only identified by amniocentesis, an invasive procedure that limits its clinical translation. Here, we aimed to evaluate whether the vaginal metabolome discriminates the presence/absence of MIAC in women with preterm labor (PTL) and intact membranes. We conducted a case-control study in women with symptoms of PTL below 34 weeks who underwent amniocentesis to discard MIAC. MIAC was defined as amniotic fluid positive for microorganisms identified by specific culture media. The cohort included 16 women with MIAC and 16 control (no MIAC). Both groups were matched for age and gestational age at admission. Vaginal fluid samples were collected shortly after amniocentesis. Metabolic profiles were analyzed by nuclear magnetic resonance (NMR) spectroscopy and compared using multivariate and univariate statistical analyses to identify significant differences between the two groups. The vaginal metabolomics profile of MIAC showed higher concentrations of hypoxanthine, proline, choline and acetylcholine and decreased concentrations of phenylalanine, glutamine, isoleucine, leucine and glycerophosphocholine. In conclusion, metabolic changes in the NMR-based vaginal metabolic profile are able to discriminate the presence/absence of MIAC in women with PTL and intact membranes. These metabolic changes might be indicative of enhanced glycolysis triggered by hypoxia conditions as a consequence of bacterial infection, thus explaining the utilization of alternative energy sources in an attempt to replenish glucose.

Characterization of the interaction of parathyroid hormone with the mitochondrial ATPase

Parathyroid hormone (PTH) has been shown to bind specifically to the beta subunit of the mitochondrial ATPase on nitrocellulose blots. We have now examined this interaction further, using intact mitochondria, submitochondrial particles, and the purified F1 ATPase. With intact mitochondria, 1 microM concentrations of PTH and its biologically active 1-34 fragment activate the ATPase about 3-fold. This effect was reduced to a 1.4-fold activation with 3-34 and 7-34 fragments of the hormone, and oxidized PTH gave no detectable activity. Activation could only be observed below pH 7. PTH had no significant effect on the activity of the purified enzyme or on submitochondrial particles. However, specific binding of an iodinated PTH analog, [Nle 8,18-Tyr 34] bPTH (1-34) amide, was found with submitochondrial particles and the purified ATPase. Binding affinity with the purified enzyme was about 10(-3) that of the plasma membrane receptor, and the molar stoichiometry was close to 1:1 (PTH:intact enzyme). With submitochondrial particles the affinity was about 10-fold higher than with the purified enzyme. This binding was further examined with PTH derivatives and fragments, and compared to that seen in the plasma membrane receptor. Oxidation of methionine 18 in PTH reduced the affinity about 50%, oxidation of methionine 8 reduced the affinity 95%, and oxidation of both methionines further decreased affinity in both membranes and submitochondrial particles. However, when compared to the native hormone, the 3-34 and 7-34 PTH fragments had much higher affinity for the submitochondrial particles than for the plasma membranes. PTH also reduced chemical crosslinking of the ATP analog, p-fluorosulfonyl benzoyl 5'-adenosine, to the alpha subunit of this enzyme, but did not alter labeling of the enzyme with 3'-O-(4'-benzoyl) benzoyl ATP, suggesting that the hormone binds near a regulatory nucleotide binding site. Direct chemical crosslinking of PTH to the beta-subunit of the enzyme was attained with a cleavable, photoactivate crosslinker, sulfosuccinimidyl 2-(p-azidosalicylamido) ethyl-1,3-dithiopropionate. The crosslinked protein was cleaved with cyanogen bromide and the labeled fragments were sequenced. The labeled fragments were found to be segments of the protein which have previously been implicated as being close to the noncatalytic ATP binding sites.