Plant sucrose-H+ symporters mediate the transport of vitamin H.
A cDNA coding for a vitamin H (biotin) transport protein from Arabidopsis was identified by genetic complementation of a biotin uptake-deficient yeast mutant. Vitamin H transport by this protein was sensitive to the SH-group inhibitor p-chloromercuribenzene sulfonic acid (PCMBS) and to the uncoupler carbonyl cyanide-m-chlorophenylhydrazone (CCCP), suggesting an energy-dependent biotin-H+ symport mechanism. The transport activity could contribute to the so-far uncharacterized plant sucrose-H+ symporter AtSUC5 which mediates the energy-dependent transport of biotin and sucrose, and restores growth of the biotin transport-deficient yeast mutant on medium with low biotin concentrations. Functional comparison of the AtSUC5 transporter with previously characterized plant sucrose or monosaccharide transporters revealed that biotin transport may be a general and specific property of all plant sucrose transporters (sucrose/biotin-H+ symporters). This first report on a transporter with dual substrate specificity for two structurally unrelated molecules has a major impact on general thinking concerning the specificity of membrane transporters. The physiological relevance of this finding is discussed.
Ludwig
A
A
Universität Erlangen-Nürnberg, Lehrstuhl Botanik II - Molekulare Pflanzenphysiologie, Staudtstrasse 5, D-91058 Erlangen, Germany.
Stolz
J
J
Sauer
N
N
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D001710:Biotin / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D005816:Genetic Complementation Test; D007700:Kinetics; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013395:Sucrose / Q000378:metabolism; D027981:Symporters
D002352:Carrier Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010940:Plant Proteins; D027981:Symporters; C119981:biotin transporter; C078729:sucrose transport protein, plant; D013395:Sucrose; D001710:Biotin