Vitamin Q

A tentatively proposed new vitamin (Q) is based on: (1) the observation that the phospholipids of the soybean contain a factor which can substitute for platelets or the clotting factor therein, as measured by the prothrombin consumption test, and (2) the finding that, with the supplementation of the diet with these phospholipids, patients having a hereditary bleeding state characterized by a moderate thrombocytopenia, a markedly defective prothrombin consumption time and a prolonged bleeding time, show a distinct improvement in the prothrombin consumption time and a normalization of the bleeding time.     

Interactions of Q beta replicase with Q beta RNA

The interactions of Qβ replicase with Qβ RNA were investigated by treating replicase-Qβ RNA complexes under various conditions with ribonuclease T₁, and by characterizing enzyme-bound RNA fragments recovered by a filter binding technique. Evidence for replicase binding at two internal regions of Qβ RNA was obtained. One region (at about 1250 to 1350 nucleotides from the 5′ end) overlaps with the initiation site for coat protein synthesis; this interaction is thought to be inessential for template activity but rather to be involved in the regulation of protein synthesis. Binding to this site (called the S-site) requires moderate concentrations of salt but no magnesium ions. The other region (at about 2550 to 2870 nucleotides from the 5′ end) is probably essential for template activity; binding to this site (called the M-site) is dependent on the presence of magnesium ions. The nucleotide sequences of the RNA fragments from the two sites were determined and found to have no common features. Under the conditions tested, replicase binding at the 3′ end of Qβ RNA could not be demonstrated, except when initiation of RNA synthesis was allowed to occur in the presence of GTP and host factor. If instead of intact Qβ RNA, a complete RNAase T₁ digest of Qβ RNA was allowed to bind to replicase, oligonucleotides from the S-site and the M-site, and oligonucleotides from a region close to the 3′ end, were found to have the highest affinity to the enzyme.The RNA fragments recovered in highest yield, M-2 and S-3 from the M and S-site, respectively, were isolated on a preparative scale and their enzyme binding properties were studied. In competition assays with random RNA fragments of the same size, selective binding was observed both for the M and the S-site fragment. Partial competition for replicase binding was found if M-2 and S-3 were presented simultaneously to the enzyme. Either fragment, if preincubated with replicase, caused a specific inhibition of initiation of Qβ RNA-directed RNA synthesis, without inhibiting the poly(rC)-directed reaction.The results are discussed in terms of a model of replicase-Qβ RNA recognition. Template specificity is attributed to binding of internal RNA regions to replicase, resulting in a specific spatial orientation of the RNA by which the inherently weak, but essential, interaction at the 3′ end is allowed to occur and to lead to the initiation of RNA synthesis.     

Q & A

Gregory A. Petsko is Gyula and Katica Tauber Professor of Biochemistry and Chemistry and Director of the Rosenstiel Basic Medical Sciences Research Center at Brandeis University. He did his undergraduate work at Princeton and his graduate work as a Rhodes Scholar at Oxford University. He held faculty positions at Wayne State University School of Medicine and MIT before moving to Brandeis in 1990. A structural biologist, he is best known for his work, together with his colleague Dagmar Ringe, on the structural basis of enzyme catalytic power and the role of protein dynamics in protein function. He writes a regular opinion column for the journal Genome Biology.     

La famille Q

Sans résuméDe l'institut néerlandais pour la recherche de l'hérédité chez l'homme et la biologie des races; section de recherche de l'hérédité médicale et statistiqueAvec 4 figures sur 1 planche     

Q & A

Leslie Orgel is a Professor and Senior Fellow at the Salk Institute in La Jolla, California, and an Adjunct Professor at the University of California at San Diego. The first part of his career was devoted to the theoretical inorganic chemistry of transition metal ions. This led to the publication of a book on Ligand-Field Theory. Since 1964, he has concentrated on aqueous solution chemistry that might be relevant to the origin of life. He has authored or co-authored two books on the origin of life.     

Non-mitochondrial coenzyme Q

The key role of coenzyme Q (ubiquinone or Q) is in mitochondrial and prokaryotic energetics. Less well investigated is the basis for its presence in eukaryotic membrane locations other than mitochondria and in plasma where both antioxidant and potentially more targeted roles are indicated. Included in the latter is that of a lipid-soluble electron transfer intermediate that serves as the transmembrane component of plasma membrane and Golgi apparatus electron transport, which regulates cytosolic NAD(+) /NADH ratios and is involved in vectorial membrane displacements and in the regulation of cell growth. Important protective effects on circulating lipoproteins and in the prevention of coronary artery disease ensue not only from the antioxidant role of CoQ(10) but also from its ability to directly block protein oxidation and superoxide generation of the TM-9 family of membrane proteins known as age-related NADH oxidase or arNOX (ENOX3) and their shed forms that appear after age 30 and some of which associate specifically with low-density lipoprotein particles to catalyze protein oxidation and crosslinking.