Oligosaccharides containing glucose and mannose in glycoproteins of the thyroid gland.

The glucose-containing oligosaccharides formed by calf thyroid slices incubated with radioactive glucose were studied. A compound soluble in chloroform/methanol/water, 1:1:0.3 (vol/vol), was found that was indistinguishable from the previously described glucose-containing dolichyl diphosphate oligosaccharide formed by liver microsomes. Glycopeptides were prepared by treating the glycoproteins with pronase, the amino acids were removed with alkaline borohydride, and the products were examined by paper electrophoresis and chromatography. A saccharide equal to that which occurs in the glucose-containing dolichyl diphosphate oligosaccharide could not be detected but glucose was found in oligosaccharides that seemed to be smaller by about three to five monosaccharide residues. The same results were obtained by direct treatment of the glycoproteins with alkaline borohydride

Characterization of a high-affinity iron transport system in Acinetobacter baumannii.

Analysis of a clinical isolate of Acinetobacter baumannii showed that this bacterium was able to grow under iron-limiting conditions, using chemically defined growth media containing different iron chelators such as human transferrin, ethylenediaminedi-(o-hydroxyphenyl)acetic acid, nitrilotriacetic acid, and 2,2'-bipyridyl. This iron uptake-proficient phenotype was due to the synthesis and secretion of a catechol-type siderophore compound. Utilization bioassays using the Salmonella typhimurium iron uptake mutants enb-1 and enb-7 proved that this siderophore is different from enterobactin. This catechol siderophore was partially purified from culture supernatants by adsorption chromatography using an XAD-7 resin. The purified component exhibited a chromatographic behavior and a UV-visible light absorption spectrum different from those of 2,3-dihydroxybenzoic acid and other bacterial catechol siderophores. Furthermore, the siderophore activity of this extracellular catechol was confirmed by its ability to stimulate energy-dependent uptake of 55Fe(III) as well as to promote the growth of A. baumannii bacterial cells under iron-deficient conditions imposed by 60 microM human transferrin. Polyacrylamide gel electrophoresis analysis showed the presence of iron-regulated proteins in both inner and outer membranes of this clinical isolate of A. baumannii. Some of these membrane proteins may be involved in the recognition and internalization of the iron-siderophore complexes