Bf. Lin et B. Shane, EXPRESSION OF ESCHERICHIA-COLI FOLYLPOLYGLUTAMATE SYNTHETASE IN THE CHINESE-HAMSTER OVARY CELL MITOCHONDRION, The Journal of biological chemistry, 269(13), 1994, pp. 9705-9713
Chinese hamster ovary (CHO) cell transfectants expressing Escherichia
coli folylpoly-gamma-glutamate synthetase (FPGS) activity solely in th
eir cytosol lack mitochondrial folylpolyglutamates and are auxotrophic
for glycine. Addition of a mammalian mitochondrial leader sequence ta
rgeted E. coli FPGS to the mitochondria of these cells. Mitochondrial
expression of FPGS restored mitochondrial folylpolyglutamate pools and
overcame the glycine requirement. Pteroyltriglutamates functioned as
effectively as the longer glutamate chain length folates found in wild
type CHO cells in the metabolic cycle of glycine synthesis provided t
hey were located in the mitochondria. Although folylpolyglutamates can
not enter the mitochondria, mitochondrial folylpolyglutamates can be r
eleased without prior hydrolysis and CHO transfectants expressing E. c
oli FPGS activity solely in the mitochondria possessed normal cytosoli
c folylpolyglutamate pools. The proportion of cellular folate in the m
itochondrion is governed by competition between mitochondrial and cyto
solic FPGS activities.