Hereditary folate malabsorption: A positively charged amino acid at position 113 of the proton-coupled folate transporter (PCFT/SLC46A1) is required for folic acid binding

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• 作者：Inbal Lasry ; Bluma Berman ; Fabian Glaser ; Gerrit Jansen ; Yehuda G. Assaraf
• 关键词：Hereditary folate malabsorption ; Folates ; Intestinal folate transport ; PCFT ; Loss-of-function mutations
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2009
• 出版时间：28 August 2009
• 年：2009
• 卷：386
• 期：3
• 页码：426-431
• 全文大小：398 K

文摘

The proton-coupled folate transporter (PCFT/SLC46A1) mediates intestinal folate uptake at acidic pH. Some loss of folic acid (FA) transport mutations in PCFT from hereditary folate malabsorption (HFM) patients cluster in R113, thereby suggesting a functional role for this residue. Herein, unlike non-conservative substitutions, an R113H mutant displayed 80-fold increase in the FA transport Km while retaining parental Vmax, hence indicating a major fall in folate substrate affinity. Furthermore, consistent with the preservation of 9 % of parental transport activity, R113H transfectants displayed a substantial decrease in the FA growth requirement relative to mock transfectants. Homology modeling based on the crystal structures of the Escherichia coli transporter homologues EmrD and glycerol-3-phosphate transporter revealed that the R113H rotamer properly protrudes into the cytoplasmic face of the minor cleft normally occupied by R113. These findings constitute the first demonstration that a basic amino acid at position 113 is required for folate substrate binding.