l-Alanine uptake in brush border membrane vesicles from the gill of a marine bivalve

Ana M. Pajor, Stephen H. Wright

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Brush border membrane vesicles were prepared from mussel gills using differential and sucrose density gradient centrifugation. These vesicles contained both the maximal Na+-dependent alanine transport activity found in the gradient and the maximal activities of γ-glutamyl transpeptidase and alkaline phosphatase. Electron micrographs showed closed vesicles of approximately 0.1-0.5 μm diameter. Transport experiments using these vesicles demonstrated a transient 18-fold overshoot in intravesicular alanine concentration in the presence of an inwardly directed Na+ gradient, but not under Na+ equilibrium conditions. A reduced overshoot (10-fold) was seen with an inwardly directed K+ gradient. Further studies revealed a broad cation selectivity, with preference for Na+, which was characteristic of alanine transport but not glucose transport in these membranes. The apparent amino acid specificity of the uptake pathway(s) was similar to that of intact gills and supported the idea of at least four separate pathways for amino acid transport in mussel gill brush border membranes. The apparent Michaelis constant for alanine uptake was approximately 7μm, consistent with values for Kt determined with intact tissue.

Original languageEnglish (US)
Pages (from-to)209-223
Number of pages15
JournalThe Journal of Membrane Biology
Volume96
Issue number3
DOIs
StatePublished - Oct 1 1987

Keywords

  • Mytilus edulis
  • alanine transport
  • brush border membrane vesicles
  • epithelia
  • integument
  • marine bivalve gills
  • neutral amino acid transport

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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