Cysteine residues in the Na+/dicarboxylate co-transporter, NaDC-1.
The role of cysteine residues in the Na(+)/dicarboxylate co-transporter (NaDC-1) was tested using site-directed mutagenesis. The transport activity of NaDC-1 was not affected by mutagenesis of any of the 11 cysteine residues, indicating that no individual cysteine residue is necessary for function. NaDC-1 is sensitive to inhibition by the impermeant cysteine-specific reagent, p-chloromercuribenzenesulphonate (pCMBS). The pCMBS-sensitive residues in NaDC-1 are Cys-227, found in transmembrane domain 5, and Cys-476, located in transmembrane domain 9. Although cysteine residues are not required for function in NaDC-1, their presence appears to be important for protein stability or trafficking to the plasma membrane. There was a direct relationship between the number of cysteine residues, regardless of location, and the transport activity and expression of NaDC-1. The results indicate that mutagenesis of multiple cysteine residues in NaDC-1 may alter the shape or configuration of the protein, leading to alterations in protein trafficking or stability.
Pajor
A M
AM
Department of Physiology, University of Texas Medical Branch, Galveston, TX 77555-0641, USA. ampajor@utmb.edu
Krajewski
S J
SJ
Sun
N
N
Gangula
R
R
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D017931:DNA Primers / Q000235:genetics; D029382:Dicarboxylic Acid Transporters; D005260:Female; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000378:metabolism; D029363:Organic Anion Transporters, Sodium-Dependent; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D027981:Symporters; D014982:Xenopus laevis
D002352:Carrier Proteins; D017931:DNA Primers; D029382:Dicarboxylic Acid Transporters; D008565:Membrane Proteins; D029363:Organic Anion Transporters, Sodium-Dependent; D011994:Recombinant Proteins; C092524:SLC13A2 protein, human; D013439:Sulfhydryl Reagents; D027981:Symporters; D002731:4-Chloromercuribenzenesulfonate; D003545:Cysteine