In vivo and in vitro anaerobic mating in Candida albicans.

Candida albicans cells of opposite mating types are thought to conjugate during infection in mammalian hosts, but paradoxically, the mating-competent opaque state is not stable at mammalian body temperatures. We found that anaerobic conditions stabilize the opaque state at 37 degrees C, block production of farnesol, and permit in vitro mating at 37 degrees C at efficiencies of up to 84%. Aerobically, farnesol prevents mating because it kills the opaque cells necessary for mating, and as a corollary, farnesol production is turned off in opaque cells.

Mechanism of 4-(beta-D-ribofuranosyl)aminobenzene 5'-phosphate synthase, a key enzyme in the methanopterin biosynthetic pathway.

The first committed step in methanopterin biosynthesis is catalyzed by 4-(beta-D-ribofuranosyl)aminobenzene 5'-phosphate (RFA-P) synthase. Unlike all known phosphoribosyltransferases, beta-RFA-P synthase catalyzes the unique formation of a C-riboside instead of an N-riboside in the condensation of p-aminobenzoic acid (pABA) and 5-phospho-alpha-D-ribosyl-1-pyrophosphate (PRPP) to produce 4-(beta-D-ribofuranosyl)aminobenzene 5'-phosphate (beta-RFA-P), CO(2), and inorganic pyrophosphate (PP(i)). Here we report the successful cloning, active overexpression in Escherichia coli, and purification of this homodimeric enzyme containing two 36.