Cellular peptide processing after a single arginyl residue. Studies on the common precursor for pancreatic polypeptide and pancreatic icosapeptide.

Cells of TM10, an established cell line, are melanocytes that contain equal amounts of eumelanin (black pigment) and pheomelanin (yellow pigment). The content of pheomelanin drastically increased when the cells were cultured in growth medium containing 0.2mM-L-dopa (L-dihydroxyphenylalanine), which is the common precursor for both eumelanogenesis and pheomelanogenesis. After this treatment, the amount of pheomelanin was 3.7-fold greater than that of control in TM10, whereas the amount of eumelanin changed very little. In contrast, 5-S-cysteinyl-dopa, which is the specific precursor for pheomelanogenesis downstream of L-dopa, did not cause preferential increase in pheomelanogenesis. Ultrastructural observations also confirmed these results; in 0.2mM-L-dopa, an increase in the number of pheomelanosomes was observed in the cytoplasm of TM10 cells. Our results also suggest that the L-dopa treatment results in a decrease in tyrosinase activity per melanosome.

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MATURATION OF THE COMMON PRECURSOR FOR BETA-ENDORPHIN AND ALPHA-MSH IN THE RAT PARS INTERMEDIA

Endogenous and Exogenous Opiate Agonists and Antagonists ◽

10.1016/b978-0-08-025488-3.50077-5 ◽

1980 ◽

pp. 293-296

Author(s):

F. Gossard ◽

P. Crine ◽

N.G. Seidah ◽

M. Chrétien

Keyword(s):

Pars Intermedia ◽

Beta Endorphin ◽

Common Precursor ◽

The Common

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Evidence for N-linked glycosylation in Toxoplasma gondii

Biochemical Journal ◽

10.1042/bj2910713 ◽

1993 ◽

Vol 291 (3) ◽

pp. 713-721 ◽

Cited By ~ 29

Author(s):

M Odenthal-Schnittler ◽

S Tomavo ◽

D Becker ◽

J F Dubremetz ◽

R T Schwarz

Keyword(s):

Toxoplasma Gondii ◽

Gel Filtration ◽

Anion Exchange Chromatography ◽

Exchange Chromatography ◽

Surface Glycoprotein ◽

Common Precursor ◽

The Common ◽

Oligosaccharide Structures

In this paper we report experiments demonstrating the presence of N-linked oligosaccharide structures in Toxoplasma gondii tachyzoites, providing the first direct biochemical evidence that this sporozoan parasite is capable of synthesizing N-linked glycans. The tachyzoite surface glycoprotein gp23 was metabolically labelled with [3H]glucosamine and [3H]mannose. Gel-filtration chromatography on Bio-Gel P4 columns produced four radiolabelled N-linked glycopeptides which were sensitive to peptidase-N-glycanase F, but resistant to endoglycosidases H and F. Using chemical analysis and exoglycosidase digestions followed by Dionex-high-pH anion-exchange chromatography and size fractionation on Bio-Gel P4 we show that gp23 has N-linked glycans in the hybrid- or complex-type structure composed of N-acetylgalactosamine, N-acetylglucosamine and mannose and devoid of sialic acid and fucose residues. In addition, the sensitivity of glycopeptides from glycoprotein extracts to endoglycosidases H and F revealed the in vivo synthesis of oligomannose-type structures by T. gondii tachyzoites. We have extended these findings by demonstrating the ability of T. gondii microsomes to synthesize in vitro a glucosylated lipid-bound high-mannose structure (Glc3Man9GlcNAc2) that is assumed to be identical with the common precursor for N-glycosylation in eukaryotes.

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