The Membrane Topology of ALMT1, an Aluminum-Activated Malate Transport Protein in Wheat (Triticum aestivum).

The wheat ALMT1 gene encodes an aluminum (Al)-activated malate transport protein which confers Al-resistance. We investigated the membrane topology of this plasma-membrane localized protein with immunocytochemical techniques. Several green fluorescent protein (GFP)-fused and histidine (His)-tagged chimeras of ALMT1 were prepared based on a computer-predicted secondary structure and transiently expressed in cultured mammalian cells. Antibodies raised to polypeptide epitopes of ALMT1 were used in conjunction with the antibody to the His-tags to determine the topology of ALMT1. This study shows that the ALMT1 protein contains six transmembrane domains with the amino and carboxyl termini located on the extracellular side of the plasma membrane.