The association of protein synthesis with formation of pigments in some photosynthetic bacteria

Abstract

NUCLEIC ACID METABOLISM IN DIVIDING LIVER 15 are not so marked as those occurring in young and foetal liver. This is to be expected by analogy with thymine catabolism. The effect of X-radiation on thymine catabolism in regenerating liver shows that, under conditions in which the formation of thymidine kinase is delayed, a delay in the depression of thymine catabolism also occurs. It is possible that the depression in thymine catabolism may be influenced by the appearance of thymidine kinase which occurs at about 18 hr. after partial hepatectomy (Bollum & Potter, 1959). When the formation of thymidine kinase is inhibited by X-radiation, the depression in thymine catabolism is delayed. SUMMARY 1. The activities of enzymes involved in nucleic acid metabolism in foetal, young and regenerating rat liver were compared with those in normal rat liver. 2. Thymidine phosphorylase and uridine phosphorylase were less active in foetal and young liver than in adult liver. Thymidine-phosphorylase activity was also reduced in regenerating liver. 3. Thymidine was incorporated into DNA in vitro more rapidly in the liver of foetal and young rats than in adult rats. 4. Dihydro-orotase activity was maximal in the liver at birth when it was twice as active as in the adult. 5. Total-body X-radiation (400 r.), when given to rats 6 hr. after partial hepatectomy, delayed the decrease in thymine catabolism.

RNA Metabolism of Rhodopseudomonas spheroides during Preferential Photopigment Synthesis

“…However, the observation that R. spheroides strain M-25 did not form bacteriochlorophyll when its RNA synthesis was restricted by deprivation of uracil suggests that RNA synthesis is necessary for bacteriochlorophyll formation. These data are consistent with a role of RNA synthesis in bacteriochlorophyll formation as already implied by the results of Sistrom (1963) and Bull & Lascelles (1963) which established that bacteriochlorophyll formation is coupled to protein synthesis. It is possible that the primary control of photopigment synthesis operates a t the genetic level by regulating synthesis of specific informational RNA required to promote synthesis of some protein integrally involved in bacteriochlorophyll synthesis.…”

“…The extent of pigment formation is inversely proportional to light intensity or to the 0, tension under semi-aerobic conditions. Formation of bacteriochlorophyll is strictly dependent upon protein synthesis (Sistrom, 1963; Bull & Lascelles, 1963). This is in part explained by the fact that certain enzymic activities associated with bacteriochlorophyll formation increase in parallel with the ability to form photopigments (Lascelles, 1959; Gibson, Neuberger & Tait, 1963).…”

Control of Chlorophyll Production in Rapidly Greening Bean Leaves

“…In Rhodopseudonionas spheroides bacterioch'lorophyll production and the activity of ALA syntheta,se, the enzyme which has been shown to catalyze the formation of ALA from glyoine and succinate in this bacterium, respond similarly to various factors: inhibitors of RNA synthesis, inhibitors of protein synthesis, light intensity, and oxygen tension (5,14,21,22,23). Consequently it appears that these environmental factors and inhibitorv compounds act on pigment synthesis by affecting this enzyme.…”

“…However, since inhibition with pulromycin was manifested initially as green patches oIn the chlorotic le,af while CAM exerted a uiniform effect, it seems likely that pturomycin is taken uip xvith more dlifficultv and is distrib;ted less evenly than CAM. DL-Ethionine (1 mam) an,d p-fluoropheinylalaniine (1 mm) inhibited chl,orophyll syn- 5. Leaves were exposed to the antimetabolites for 16 hours prior to exposure to light.…”

Rhodobacter capsulatus puf operon encodes a regulatory protein (PufQ) for bacteriochlorophyll biosynthesis.

“…6). This conclusion is based, in part, on the observations that when photosynthetically growing cells are subjected to environmental shifts, such as the introduction of oxygen (7), high light intensity (7), or inhibitors ofprotein synthesis (8,9), there is an abrupt cessation of BChl biosynthesis that is too rapid to simply be attributed to inhibiting the synthesis of enzymes in the BChl biosynthetic pathway. In addition, classical forms of regulation such as feedback inhibition by BChl or its precursors do not occur (6,(10)(11)(12).…”