Functional analysis of mutations in the glucose-6-phosphate transporter that cause glycogen storage disease type Ib.
The glucose-6-phosphate transporter (G6PT) deficient in glycogen storage disease type Ib is a phosphate (P(i))-linked antiporter capable of G6P: P(i) and P(i):P(i) exchanges. We previously characterized G6PT mutations by measuring G6P uptake activities in microsomes co-expressing G6PT and glucose-6-phosphatase-alpha. Here we report a new assay, based on reconstituted proteoliposomes carrying only G6PT, and characterize G6P and P(i) uptake activities of 23 G6PT mutations. We show that co-expression and G6PT-only assays are equivalent in measuring G6PT activity. However, the p.Q133P mutation exhibits differential G6P and P(i) transport activities, suggesting that characterizing G6P and P(i) transport activities of G6PT mutations may yield insights to this genetic disorder.
Section on Cellular Differentiation, Program on Developmental Endocrinology and Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Building 10, Room 9D42, NIH 10 Center Drive, Bethesda, MD 20892-1830, USA.
Shih-Yin
SY
Chen
Chi-Jiunn
CJ
Pan
Soojung
S
Lee
Wentao
W
Peng
Janice Y
JY
Chou
D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002522:Chlorocebus aethiops; D019298:Glucose-6-Phosphate / Q000378:metabolism*; D005953:Glycogen Storage Disease Type I / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008861:Microsomes / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation; D010710:Phosphates / Q000378:metabolism
D009004:Monosaccharide Transport Proteins; D010710:Phosphates; D019298:Glucose-6-Phosphate