The variable carhoxy! terminus of the plasma membrane, ('a pump contains a unique regula'ory region: it lias a high afhnii) calmodulin-binding domain and target site; tor pliosphorylation with protein kinases A and ('. The great di versity of this region indicates that the different isoforms of the pump will have different regulatory characteristics. Recently, we have suggested that hPMCAla, unlike hPMCA-lh. has a two-part calmodulin-binding domain separated by a short non-binding region. Here we studied further the regulation of hPMCA ta expressed in t IK- COS cell system j with protein kinase C. Kxperintents with iMim'a'ed mutants of this i sofort u indicated that pliosphorylation with the kinai-.e occur.-, between residues 1 and 112. The only residue that could become pho-phorylated within this region is serine 11 In. Indeed, a point mut at ion in which erine 11 to was < hanged 1 o alanine did not show phosphoivlation. 'Mm-, we identified ;i unique phosphoivlation Mtp in hPMCAla. An important aspect of t h U pho.sphorylation site is that while it lies within the extended calrnodulin binding domain of this iM>forrn. its phosphorylation did not affect i alrmxiiilin binding,. Only a minor snif' in the calmodulin response curve of hPMCA-la was observed when phosphoiyhition was miinicked by converting serine . This finding is in good agreement with the notion that serine lies within the region of the calmoduln binding domain that is folded out of the calmodulin-pump interation surface.
|Publication status||Published - Dec 1 1998|
ASJC Scopus subject areas
- Molecular Biology