9.A.20 The Low Affinity Cation Transporter (LACatT) Family

A single member of the LACatT family has been sequenced and functionally characterized. This protein, LCT1 of Triticum aestivum (wheat), possesses about 570 amino acyl residues, 10 or 11 putative transmembrane α-helical spanners (TMSs) and a 200 residue hydrophilic amino terminus containing sequences enriched in proline, glutamate, serine and threonine (PEST). The transporter was shown to mediate low affinity (~10 mM) uptake of K , Rb , Na , Ca2 and Cd2 , but not Zn2 , in a yeast mutant strain deficient in K uptake. Several divalent metal ions (Mn2 , Zn2 , Pb2 , Cu2 ) inhibit transport. LCT1 is expressed in low abundance in wheat roots and leaves. The mode of transport and energy coupling mechanism (if any) are not known. A homologue is present in rice.

The generalized transport reaction believed to be catalyzed by LCT1 is:

cation (out) cation (in)


 

References:

Clemens, S., D.M. Antosiewicz, J.M. Ward, D.P. Schachtman and J.I. Schroeder (1998). The plant cDNA LCT1 mediates the uptake of calcium and cadmium in yeast. Proc. Natl. Acad.Sci. USA, in press.

Hall, A.M., B.M. Wiczer, T. Herrmann, W. Stremmel, and D.A. Bernlohr. (2005). Enzymatic properties of purified murine fatty acid transport protein 4 and analysis of acyl-CoA synthetase activities in tissues from FATP4 null mice. J. Biol. Chem. 280: 11948-11954.

Schachtman, D.P., R. Kumar, J.I. Schroeder and E.L. Marsh (1997). Molecular and functional characterization of a novel low-affinity cation transporter (LCT1) in higher plants. Proc. Natl. Acad. Sci. USA 94: 11079-11084.

Stuhlsatz-Krouper, S.M., N.E. Bennett, and J.E. Schaffer. (1998). Substitution of alanine for serine 250 in the murine fatty acid transport protein inhibits long chain fatty acid transport. J. Biol. Chem. 273: 28642-28650.

Stuhlsatz-Krouper, S.M., N.E. Bennett, and J.E. Schaffer. (1999). Molecular aspects of fatty acid transport: mutations in the IYTSGTTGXPK motif impair fatty acid transport protein function. Prostaglandins Leukot. Essent. Fatty Acids 60: 285-289.

Zou, Z., C.C. DiRusso, V. Ctrnacta, and P.N. Black. (2002). Fatty acid transport in Saccharomyces cerevisiae. Directed mutagenesis of FAT1 distinguishes the biochemical activities associated with Fat1p. J. Biol. Chem. 277: 31062-31071.

Examples:

TC#NameOrganismal TypeExample
9.A.20.1.1Low affinity cation transporter, LCT1 Plants LCT1 of Triticum aestivum (AAB71851)