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Nongastric H,K‐ATPase: Structure and Functional Properties
Author(s) -
MODYANOV NIKOLAI,
PESTOV NIKOLAY,
ADAMS GAIL,
CRAMBERT GILLES,
TILLEKERATNE MANORANJANI,
ZHAO HAO,
KORNEENKO TATYANA,
SHAKHPARONOV MIKHAIL,
GEERING KATHI
Publication year - 2003
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.2003.tb07158.x
Subject(s) - xenopus , biophysics , atpase , chemistry , ouabain , biochemistry , microbiology and biotechnology , biology , enzyme , sodium , organic chemistry , gene
A bstract : Nongastric H,K‐ATPases whose catalytic subunits (AL1) encoded by human ATP1AL1 and homologous animal genes comprise the third distinct group within the X,K‐ATPase family. No unique nongastric β has been identified. Precise in situ colocalization and strong association of AL1 with β1 of Na,K‐ATPase was detected in apical membranes of rodent prostate epithelium. In this tissue, β1NK serves as an authentic subunit of both the Na,K‐ and nongastric H,K‐pumps. Upon expression in Xenopus oocytes the human AL1 can assemble with β1NK, and more efficiently with gastric βHK, into functional H,K‐pumps. Both AL1/β complexes exhibit a similar K‐affinity, and their K‐transport depends on intra‐ and extracellular Na. These data provide new evidence that nongastric H,K‐ATPase can perform Na/K‐exchange, and indicate that β does not significantly affect this ion‐pump function. Analysis of human nongastric H,K‐ATPase expressed in Sf‐21 insect cells revealed that AL1/βHK exhibits substantial enzymatic activities in K‐free medium and K stimulates, but Na has inhibitory effect on ATP hydrolysis. Thus, although the nongastric H,K‐ATPase can function as Na/K exchanger, its reaction mechanism is different from that of the Na,K‐ATPase. Human nongastric H,K‐ATPase is highly sensitive to bufalin, digoxin, and digitoxin, but almost resistant to digoxigenin and ouabagenin.