Antiserum against Cl- pump complex recognizes 51 kDa protein, a possible catalytic unit in the rat brain

We purified Cl- pump in the rat brain and obtained 520 or 580 kDa protein c omplexes which consisted of 62, 60, 55 and 51 kDa proteins. An antiserum ag ainst 520 kDa protein complex recognized 51 kDa protein in both 520 and 580 kDa complexes, and reduced both Cl--ATPase and Cl- pump activities. Such a n immunoreactive 51 kDa protein was found in the brain, spinal cord and kid ney. When incubated with [gamma-P-32]ATP, the protein complex yielded phosp horylated 51 kDa protein, the label being hydroxylamine-sensitive and incre ased in the presence of CT and/or an inhibitor of Cl- pump, ethacrynic acid . Thus, the antibody appears to recognize a possible catalytic subunit of C l- pump, 51 kDa protein, in the rat. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.