The occurrence of serotonin-containing cells in the esophageal epithelium of the bullfrog Rana catesbeiana: a fluorescence histochemical and immunohistochemical study

Fluorescence histochemical examination of biogenic amines of the frog esophageal mucosa revealed that a serotonin-like monoamine exhibiting an yellow fluorescence was present in a certain type of cells. The new type of cells was specifically stained by the immunohistochemical method using anti-serotonin antiserum. From these observations, it is suggested that the new cell type in the esophageal mucosa probably contains 5-hydroxytryptamine (serotonin). The serotonin-containing cells were argentaffin, but negative for Grimelius' silver stain.     

The VIG9 gene products from the human pathogenic fungi Candida albicans and Candida glabrata encode GDP-mannose pyrophosphorylase

We have identified two genomic DNA fragments from the human pathogenic fungi, Candida albicans (CaVIG9) and Candida glabrata (CgVIG9) that encode GDP-mannose pyrophosphorylase, a key enzyme for protein glycosylation. The VIG9 homologues of CaVIG9 and CgVIG9 complement an identified protein glycosylation-defective mutation, vig9, of Saccharomyces cerevisiae. The nucleotide sequences of the ORFs, which are 83 and 90% identical to that of the ScVIG9 protein, respectively, showed a predicted gene product homologous to S. cerevisiae GDP-mannose pyrophosphorylase. We examined the enzyme activity of a glutathione S-transferase fusion of each VIG9 gene to synthesize GDP mannose in the cell extracts of a heterologous Escherichia coli expression system. We also developed a method for detecting the enzyme activity using a non-radioactive substrate that would be applicable to high throughput screening.     

Distinct structures of ATP and GTP complexes in the myosin ATPase

The active site of the myosin subfragment-1 ATPase was affinity-labeled with ribose-modified fluorescent analogs of ADP, dADP, CDP, UDP, IDP, and GDP in combination with vanadate, forming a stable myosin-nucleoside diphosphate-vanadate complex that is analogous to the normal myosin-ADP-Pi intermediate [Hiratsuka, T. (1984) J. Biochem. 96, 147-154]. Labeled enzyme was isolated free of unbound analog and vanadate, and fluorescent properties of the fluorophore at the active site were examined. Fluorescence emission and acrylamide quenching studies revealed that the hydrophobicity of environment around the fluorophore and the degree of its burial in the protein vary with the base structure of NDP. It was found that the fluorophore of ADP analog is most buried into the protein, while that of the GDP analog is least buried. The results suggest that the deep burial of ATP into the myosin active site is essential for muscle contraction.