Isolation and characterization of a cDNA encoding the putative distal colon H+,K(+)-ATPase. Similarity of deduced amino acid sequence to gastric H+,K(+)-ATPase and Na+,K(+)-ATPase and mRNA expression in distal colon, kidney, and uterus.
A series of Northern blot hybridization experiments using probes derived from the rat gastric H+,K(+)-ATPase cDNA and the human ATP1AL1 gene revealed the presence of a 4.3-kilobase mRNA in colon that seemed likely to encode the distal colon H+,K(+)-ATPase, the enzyme responsible for K+ absorption in mammalian colon. A rat colon library was then screened using a probe from the ATP1AL1 gene, and cDNAs containing the entire coding sequence of a new P-type ATPase were isolated and characterized. The deduced polypeptide is 1036 amino acids in length and has an Mr of 114,842. The protein exhibits 63% amino acid identity to the gastric H+,K(+)-ATPase alpha-subunit and 63% identity to the three Na+,K(+)-ATPase alpha-subunit isoforms, consistent with the possibility that it is a K(+)-transporting ATPase. Northern blot analyses show that the 4.3-kilobase mRNA is expressed at high levels in distal colon; at much lower levels in proximal colon, kidney, and uterus; and at trace levels in heart and forestomach. The high mRNA levels in distal colon and the similarity of the colon pump to both gastric H+,K(+)- and Na+,K(+)-ATPases suggest that it is the distal colon H+,K(+)-ATPase. Furthermore, expression of its mRNA in kidney raises the possibility that the enzyme also corresponds to the H+,K(+)-ATPase that seems to play a role in K+ absorption and H+ secretion in the distal nephron.
Crowson
M S
MS
Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Ohio 45267-0524.
Shull
G E
GE
D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D003106:Colon / Q000201:enzymology*; D004247:DNA / Q000235:genetics / Q000302:isolation & purification*; D005260:Female; D017506:H(+)-K(+)-Exchanging ATPase; D007668:Kidney / Q000201:enzymology; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics* / Q000378:metabolism; D013270:Stomach / Q000201:enzymology*; D014018:Tissue Distribution; D014599:Uterus / Q000201:enzymology
D012333:RNA, Messenger; D004247:DNA; D000251:Adenosine Triphosphatases; D017506:H(+)-K(+)-Exchanging ATPase; D000254:Sodium-Potassium-Exchanging ATPase