Deletions in the A(L) region of the h4xb plasma membrane Ca(2+) pump. High apparent affinity for Ca(2+) of a deletion mutant resembling the alternative spliced form h4zb.
Mutants of the plasma membrane Ca(2+) pump (human isoform 4xb) with deletions in the linker between domain A and transmembrane segment M3 (A(L) region) were constructed and expressed in Chinese hamster ovary cells. The total or partial removal of the amino acid segment 300-349 did not change the maximal Ca(2+) transport activity, but mutants with deletions involving residues 300-338 exhibited a higher apparent affinity for Ca(2+) than the wild type h4xb enzyme. Deletion of the putative acidic lipid interacting sequence (residues 339-349) had no observable functional consequences. The removal of either residues 300-314 or 313-338 resulted in a similar increase in the apparent Ca(2+) affinity of the pump although the increase was somewhat lower than that obtained by the deletion 300-349 suggesting that both deletions affected the same structural determinant. The results show that alterations in the region of the alternative splicing site A change the sensitivity to Ca(2+) of the human isoform 4 of the PMCA.
IQUIFIB-Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires Junín 956, 1113 Buenos Aires, Argentina.
Felicitas
F
de Tezanos Pinto
Hugo P
HP
Adamo
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D053499:Plasma Membrane Calcium-Transporting ATPases; D017434:Protein Structure, Tertiary; D022821:RNA Splice Sites / Q000235:genetics*; D017384:Sequence Deletion
D027682:Cation Transport Proteins; D007527:Isoenzymes; D022821:RNA Splice Sites; D053499:Plasma Membrane Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium