Biomedical subjects
Publications and source records attributed to E Yokota.
A beta-lactamase from Branhamella catarrhalis was purified by column chromatography. The purified enzyme hydrolyzed penicillins, such as ampicillin, carbenicillin, and piperacillin, more rapidly than cephalosporins. Furthermore, the enzyme hydrolyzed cefotaxime and cefmenoxime. The molecular weight of the enzyme was 33,000. The pI was 5.4.
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Hemocyanins are large multi-subunit copper proteins that transport oxygen in many arthropods and molluscs. Comparison of the amino acid sequence data for seven different subunits of arthropod hemocyanins from crustaceans and chelicerates shows many highly conserved residues and extensive regions of near identity. This correspondence can be matched closely with the three domain structure established by x-ray crystallography for spiny lobster hemocyanin. The degree of identity is particularly striking in the second domain of the subunit that contains the six histidines which ligate the two oxygen-binding copper atoms. The polypeptide architecture of spiny lobster hemocyanin appears to be the same in all arthropods. This structure must therefore be at least as old as the estimated time of divergence of crustaceans and chelicerates, about 540 to 600 million years ago.
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The amino acid sequence of the largest CNBr fragment, CNBrIa, from hemocyanin II of Limulus polyphemus has been determined. This fragment contains 203 residues, has Mr = 23,600, and is the NH2-terminal segment of the molecule. Comparison of this sequence with the first 87 residues of the NH2-terminal sequence of the alpha chain of hemocyanin from the Japanese horseshoe crab, Tachypleus tridentatus, of the Western Pacific (Nemoto, T., and Takagi, T. (1981) Biochim. Biophys. Acta 670, 79-83) shows that 46% of the residues are identical. Residues 172-177, -His-His-Trp-His-Trp-His-, appear to constitute at least part of the copper-binding site. This conclusion is supported by our finding that 40% of the residues in the sequence 172-186 are identical to residues 188-202 in tyrosinase from Neurospora; residues 188 and 193 in tyrosinase are known to be copper-binding histidines (Pfiffner, E., and Lerch, K. (1981) Biochemistry 20, 6029-6035). Model building suggests that histidines 172 and 175 might bind one copper atom and histidines 173 and 177 might bind the second copper. These observations suggest that tyrosinase and hemocyanin may have a common evolutionary origin, but we have not so far seen other correspondences.
We report the rare occurrence of sicca syndrome associated with primary amyloidosis. A 63-year-old man with apparent keratoconjunctivitis sicca and xerostomia died of the cardiac failure. Neither sialography nor labial gland biopsy revealed findings compatible with Sjögren's syndrome. Macroglobulinemia and a positive Bence-Jones protein were noted in urine testing. Amyloid deposition was demonstrated by Congo red staining on biopsied rectal tissues, and by typical birefringence under polarized light microscopy. At autopsy, the amyloid deposition was identified histochemically in the submandibular gland and the minor salivary glands of oral cavity.
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By using isolated actin bundles of brush border microvilli of chicken intestinal epithelial cells, it was clearly visualized that muscle beta-actinin caps the pointed end of an actin filament, whereas cytochalasin D masks the barbed end. The growth rate at the barbed end in the presence of beta-actinin was markedly slower than in its absence.
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