SHORT COMMUNICATIONS 27c photoreduction procedure produces other minor components (Cerutti et al. 1966), the major reaction is the conversion of uridylic acid into dihydrouridylic acid. The hydrated oligonucleotide offers the advantage, which was kindly pointed out to us by Professor D. Shugar, that the 5-hydro-6hydroxyuridylic acid can be specifically reconverted into uridylic acid on heating (Sinsheimer, 1954). Table 1 shows that, not only is the s-RNA binding capacity ofApUpG destroyed by converting uridylic acid into 5-hydro-6-hydroxyyuridylic acid, but the effect is completely reversed on heating, proving that the loss of activity is not due to other reactions or degradation of the oligonucleotide. 5-Hydro-6-hydroxyuridylic acid would be expected to have the same template properties as dihydrouridylic acid. Grossman (1963) has reported that u.v.-irradiated polyU, comprising uracil dimers, uridylic acid and 5-hydro-6-hydroxyuridylic acid, incorporates serine as well as having a decreased phenylalanine incorporation, which is in contrast with poly(U,H2U), which only has a decreased incorporation of phenylalanine relative to polyU (Rottman & Cerutti, 1966). However, although Grossman (1963) attributed the serine incorporation to the 5-hydro-6-hydroxyuridylic acid, because of the behaviour of the copolymer after irradiation at different wavelengths, it is possible that the serine incorporation was due to chain scission (Logan &;Whitmore, 1966), rather than a template difference between uridylic acid and its hydrate.The experiments reported here show that when ApUpG is converted into either ApH2UpG or Ap(H20)UpG the triplet loses its ability to bind methionyl-s-RNA. These results are compatible with the idea that the interconversion of uridylic acid and dihydrouridylic acid in a chain-initiating coding triplet could be involved in the regulation of protein synthesis at the translational level.
1. When Bacillus cereus 569/H was grown in a casamino acid (casein-hydrolysate) medium containing zinc sulphate rapid production of extracellular beta-lactamase II preceded that of beta-lactamase I. 2. beta-Lactamase I was separated from beta-lactamase II by fractional precipitation with ammonium sulphate. 3. beta-Lactamase I was purified by a process involving chromatography on Celite and DEAE-cellulose and beta-lactamase II by chromatography on DEAE-cellulose after denaturation of beta-lactamase I by heat. Both enzymes were obtained in crystalline form. 4. beta-Lactamase II prepared in this way appeared to have a higher molecular weight than beta-lactamase I and required Zn(2+) as a cofactor for both cephalosporinase and penicillinase activities.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.