Human pituitary extracts were fractionated by chromatography on Sephadex G-50 and G-25, and low molecular weight components were further separated by HPLC. Eluates were tested for their activity in stimulating steroidogenesis in suspensions of rat adrenal capsule (largely zona glomerulosa) and inner zone (fasciculata/reticularis) cells. Several biologically active components were reproducibly isolated. Three stimulated glomerulosa cells specifically, and one of these was tentatively identified by HPLC and RIA criteria as desacetyl-alpha-MSH. Alpha-MSH was not detected. One component stimulated both cell types but two others stimulated inner zone cells, and were without effect on glomerulosa cells: this type of activity has not previously been described, and is not associated with any peptide derived from pro-opiomelanocortin which has so far been tested. The data suggest that, in addition to corticotrophin, further pituitary peptides may be involved in the control of adrenocortical function.

Adrenal Glands↗

PubMedDate not supplied

Hallmarks of Caenorhabditis elegans N-glycosylation: complexity and controversy.

Caenorhabditis elegans has become one of the most widely used model organisms for a range of molecular cell biological applications and is being increasingly used by glycobiologists. However, a major problem has been the lack of knowledge of the structure of the protein-linked glycans from this organism. In recent years several groups have published structural data, particularly N-glycan structural data. However, some of these data are contradictory. In this review we critically assess all the N-glycan structural data and consider how close we are in our goal of defining the glycome of C. elegans.

Animals↗

PubMedDate not supplied

Primary structure of a chloramphenicol acetyltransferase specified by R plasmids.

Naturally occurring isolates of chloramphenicol-resistant bacteria commonly synthesise chloramphenicol acetyltransferase (EC 2.3.28; CAT) in amounts which are sufficient to account for the resistance phenotype and often harbour plasmids which carry the structural gene for CAT. The findings of CAT in such diverse prokaryotes as Proteus mirabilis, Agrobacterium tumefaciens, Streptomyces sp., and a soil Flavobacterium has led to speculation concerning the origin and evolution of the more commonly observed CAT variants specified by plasmids in clinically important bacteria. To provide a more solid basis for studying the evolution and spread of CAT within prokaryotes we chose to determine the complete amino acid sequence of a type I variant of CAT, the variant known to be associated with most F-like plasmids conferring chloramphenicol resistance. The sequence has been determined by combining the results obtained from manual and automated sequential degradation with those obtained by mass spectrometry of peptides generated by enzymatic digestion. The directly determined primary structure is identical with that predicted by the DNA sequence analysis of the chloramphenicol resistance transponson Tn9 known to specify a type I variant of chloramphenicol acetyltransferase.

Acetyltransferases↗

PubMedDate not supplied

Glucan synthesis in Pneumocystis carinii.

Rat-derived Pneumocystis carinii lysed with sodium deoxycholate catalysed the incorporation of uridine diphosphoglucose into an insoluble polymer. This enzyme activity was present in both the pellet and the supernatant when the P. carinii preparations were centrifuged. The polymer whose production was catalysed by the supernatant was examined by mass spectrometry and found to be an alpha 1----4 glucan, which is either unbranched or has relatively few branches. Polymer formation was completely inhibited by the addition of alpha amyloglucohydrolase to the supernatant. Polymer formation in the pellet of deoxycholate P. carinii preparations, unlike that in the supernatant, was partially resistant to alpha amyloglucohydrolase. The soluble glucan synthase activity in the supernatant was stable for more than 30 h at room temperature and was approximately 50 times more active on a cell-to-cell basis than the supernatant from deoxycholate preparations of the yeast Saccharomyces cerevisae.

Animals↗