Identification of a putative Na(+)-H+ exchanger regulatory cofactor in rabbit renal BBM

Am J Physiol. 1990 Dec;259(6 Pt 2):F867-71. doi: 10.1152/ajprenal.1990.259.6.F867.


Previous in vitro studies with detergent-solubilized rabbit renal brush-border membrane (BBM) proteins have suggested that adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase A (PKA)-mediated inhibition of the Na(+)-H+ exchanger requires the presence of 42-kDa cofactor that is distinct from the exchanger itself. We sought to determine whether there was a protein in native rabbit renal BBM vesicles that has characteristics similar to that of the 42-kDa cofactor. Incubation of native BBM vesicle proteins with a hypotonic phosphorylation solution containing purified catalytic subunit of PKA resulted in phosphorylation of a number of BBM proteins, including a protein with an apparent molecular weight that was similar but not identical to that of the 42-kDa cofactor obtained from anion-exchange column chromatography of n-octyl glucoside-extracted BBM proteins. The identity between the BBM vesicle protein and the 42-kDa cofactor was established by phosphopeptide maps and radioiodinated peptide maps. These results indicate that native BBM vesicles contain a number of proteins that are phosphorylated by PKA when the PKA and ATP are present inside the vesicle space. One of these proteins appears to be identical to the 42-kDa protein that, as previously suggested by in vitro studies, acts as a regulatory cofactor mediating the inhibitory effect of PKA on the renal Na(+)-H+ exchanger.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Animals
  • Autoradiography
  • Carrier Proteins / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Kidney / metabolism*
  • Magnesium / metabolism
  • Microvilli / metabolism
  • Peptide Mapping
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Protein Kinases / metabolism
  • Rabbits
  • Sodium-Hydrogen Exchangers


  • Carrier Proteins
  • Phosphoproteins
  • Sodium-Hydrogen Exchangers
  • Adenosine Triphosphate
  • Protein Kinases
  • Magnesium