Heptaprenyl diphosphate synthase of Bacillus subtilis, which participates in the biosynthesis of the side chain of menaquinone-7, is composed of two dissociable subunits, component I and component II, which are encoded by two cistrons in a novel gene cluster of gerC operon [Zhang, Y.-W., et al. (1997) J. Bacteriol. 179, 1417-1419]. This enzyme essentially requires the coexistence of both subunits for its catalysis. Expression vector systems for the two structural genes, gerC1 and gerC3, were constructed separately, and the two components were overproduced in Escherichia coli cells. After purification, their dynamic interactions in forming a catalytically active complex were investigated by gel filtration and immunoblotting analyses. When a mixture of the two components that had been preincubated in the presence of Mg2+ and farnesyl diphosphate was subjected to Superdex 200 gel filtration, a significant elution peak appeared in a region earlier than those observed when they were chromatographed individually. This fraction contained both components I and II, and it corresponded to a molecular mass that is in accord with the sum of the values of the two components. Cross-linking studies indicate that the two essential subunits, farnesyl diphosphate, and Mg2+ form a ternary complex which seems to represent a catalytically active state of the heptaprenyl diphosphate synthase. On the other hand, no complex was formed in the presence of isopentenyl diphosphate or inorganic pyrophosphate and Mg2+. A photoaffinity analogue of farnesyl diphosphate was shown to preferentially label the component I protein, suggesting that component I possesses a specific affinity for the allylic substrate. Furthermore, the photoaffinity labeling of component I significantly increased in the presence of component II. The mechanism of catalysis of this unique heteromeric enzyme is understood by assuming that association and dissociation of the two subunits facilitate turnover of catalysis for the synthesis of the amphipathic product from soluble substrates.
Candida chorioamnionitis is rare but can lead to neonatal infection, high mortality, and neurodevelopmental impairment. We aimed to investigate maternal clinical features and perinatal outcomes and discuss future management strategies. We reviewed the medical records of women with Candida chorioamnionitis at our hospital over a 10-year period (n = 9) and previous published case reports and case series. The most prevalent Candida species was C. albicans (71.3% of the all cases). The most prevalent predisposing condition was preterm premature rupture of membranes (31/123, 25.2%), followed by pregnancy with a retained intrauterine contraceptive device (26/123, 21.1%) and pregnancy after in vitro fertilization (25/123, 20.3%). Preterm labor was the most common symptom (52/123, 42.3%), and only 13% of cases involved fever. Of the infants, 27% of the singletons and 23.8% of the twins were born before 22 gestational weeks, while 60% of the singletons and 76.2% of the twins were born at 22–36 weeks. The median birth weight of the babies born after 22 weeks was 1230 g. The mortality rates of the singletons and twins born after 22 weeks of gestation in the year 2000 or later were 28.6% and 52.4%, respectively. Antenatal treatment for Candida chorioamnionitis has not been established.
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