| 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)
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| 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.
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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.
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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.
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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.
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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.
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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.
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| Examples: |
| TC# | Name | Organismal Type | Example |
| 9.A.20.1.1 | Low affinity cation transporter, LCT1 | Plants | LCT1 of Triticum aestivum (AAB71851) |
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