The class I E. coli ribonucleotide reductase, composed of homodimers of R1 and R2, catalyzes the conversion of nucleoside diphosphates to deoxynucleoside diphosphates. The reduction process involves the tyrosyl radical on R2 that generates a transient thiyl radical on R1 over a proposed distance of 35 A. A mechanism-based inhibitor, 2'-azido-2'-deoxyuridine-5'-diphosphate, that reduces the tyro...

Addition of the nucleoside diphosphates CDP, UDP, TDP, and IDP to intact, respiring, rat liver mitochondria immediately following ATP formation results in a marked stimulation of respiration at all concentrations of nucleotide tested. Addition of GDP stimulates respiration when added at concentrations below 150 PM, whereas at higher concentrations this nucleotide has much less effect on respira...

Extensively purified rat liver cytosolic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase kinase was used to examine the role of ADP in inactivation of HMG-CoA reductase (EC 1.1.1.34). Solubilized HMG-CoA reductase was a suitable substrate for HMG-CoA reductase kinase. At sufficiently high concentrations of solubilized HMG-CoA reductase, reductase kinase activity approached that measur...

Reis (1) discovered 5’-nucleotidase in 1934. Shortly thereafter, Gulland and Jackson (2) showed its presence in venoms of many species of snake. Although several methods of separation of 5’-nucleotidase from phosphodiesterase of venom have been proposed (3-7), the available preparations of 5’-nucleotidase are still rather crude (8-10). Two reasons prompted us to purify venom 5’-nucleotidase. Fi...

Reis (1) discovered 5’-nucleotidase in 1934. Shortly thereafter, Gulland and Jackson (2) showed its presence in venoms of many species of snake. Although several methods of separation of 5’-nucleotidase from phosphodiesterase of venom have been proposed (3-7), the available preparations of 5’-nucleotidase are still rather crude (8-10). Two reasons prompted us to purify venom 5’-nucleotidase. Fi...

"Head-to-head" terpene synthases catalyze the first committed steps in sterol and carotenoid biosynthesis: the condensation of two isoprenoid diphosphates to form cyclopropylcarbinyl diphosphates, followed by ring opening. Here, we report the structures of Staphylococcus aureus dehydrosqualene synthase (CrtM) complexed with its reaction intermediate, presqualene diphosphate (PSPP), the dehydros...