Uptake of lysine and proline via separate α-neutral amino acid transport pathways in Mytilus gill brush border membranes

Ana M. Pajor, Stephen H. Wright

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Brush border membrane vesicles (BBMV) were prepared from the gills of the marine mussel, Mytilus edulis. These membranes contained two distinct pathways for cotransport of Na+ and α-neutral amino acids. The major pathway in mussel gill BBMV was the alanine-lysine (AK) pathway, which had a high affinity for alanine and for the cationic amino acid, lysine. The AK pathway was inhibited by nonpolar α-neutral amino acids and cationic amino acids, but was not affected by β-neutral amino acids or imino acids. The kinetics of lysine transport were consistent with a single saturable process, with a Jmax of 550 pmol/mg-min and a Kt of 5 μm. The AK pathway did not have a strict requirement for Na+, and concentrative transport of lysine was seen in the presence of inwardly directed gradients of Li+ and K+, as well as Na+. Harmaline inhibited the transport of lysine in solutions containing either Na+ or K+. The alanine-proline (AP) pathway transported both alanine and proline in mussel gill BBMV. The AP pathway was strongly inhibited by nonpolar α-neutral amino acids, proline, and α-(methylamino)isobutyric acid (Me-AIB). The kinetics of proline transport were described by a single saturable process, with a Jmax of 180 pmol/mg-min and Kt of 4 μm. In contrast to the AK pathway, the AP pathway appeared to have a strict requirement for Na+. Na+-activation experiments with lysine and proline revealed sigmoid kinetics, indicating that multiple Na+ ions are involved in the transport of these substrates. The transport of both lysine and proline was affected by membrane potential in a manner consistent with electrogenic transport.

Original languageEnglish (US)
Pages (from-to)237-247
Number of pages11
JournalThe Journal of Membrane Biology
Issue number3
StatePublished - Mar 1 1989



  • Mytilus edulis
  • Na-cotransport
  • alanine transport
  • brush-border membrane vesicles
  • lysine transport
  • proline transport

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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