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Structure‐function activity of the human sodium‐dependent multivitamin transporter (hSMVT): Role of Histidine (His) residues
Author(s) -
Ghosal Abhisek,
Said Hamid M
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.657.3
Biotin, a water‐soluble vitamin, is essential for normal growth and well‐being. Humans must obtain biotin from external sources via the intestine, a process that involves the apically expressed SMVT. Little is known about structure‐function activity relationship of SMVT. Using site‐directed mutagenesis, we examined the role of conserved His residues in hSMVT in transporting the negatively charged biotin. Of the seven conserved His residues, only His 115 and His 254 were found to be important for functionality as their mutation caused a significant reduction in carrier‐mediated biotin uptake. Kinetic studies showed the inhibition to be mediated via a significant reduction in the Vmax, but not the apparent Km, of the biotin uptake process. The inhibition was not related to the charge of the His residue or due to changes in transcriptional/translational efficiency of the mutated hSMVT compared to wild‐type hSMVT. Surface biotinylation showed a significant reduction in cell surface expression of the mutated hSMVT, a finding which was further confirmed by confocal imaging. Our results show important role for His 115 and His 254 residues in the functionality of hSMVT. (Supported by grants from the DVA and the NIH)