New Ca2+ pump isoforms generated by alternative splicing of rPMCA2 mRNA.
Alternative splices capable of generating proteins with altered functions were found (by PCR) in isoform 2 of the rat plasma membrane Ca2+ pump. These splices were concentrated in two hypervariable regions. One of these regions, near the N-terminus and the lipid-binding region, could be altered by the insertion of either or both of inserts x and y. Insertion of both x and y would add 45 amino acids to the molecule. The y insert causes the appearance of a rather hydrophobic stretch of amino acids in the middle of a highly polar region. The second variable region begins in the middle of the calmodulin-binding domain. Insertion of 229 nucleotides at this point of the message converts the b form to the a form, which has an altered (and shorter) C-terminus. The calmodulin-binding domain of this shortened form has a less basic character, which would decrease the affinity for calmodulin. The b form of isoenzyme 2 contains relatively weak protein kinase A substrate sequences, such as KQNSS and KNNS. These sequences are eliminated in form a, and a strongly activated kinase substrate sequence, RRQSS, appears in a different place. Different tissues use different combinations of alternative splices, with heart and brain showing the greatest diversity.
Adamo
H P
HP
Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905.
Penniston
J T
JT
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000201:enzymology; D000252:Calcium-Transporting ATPases / Q000235:genetics*; D005260:Female; D005809:Genes, Regulator; D007527:Isoenzymes / Q000235:genetics*; D007668:Kidney / Q000201:enzymology; D008969:Molecular Sequence Data; D009206:Myocardium / Q000201:enzymology; D011487:Protein Conformation; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D011919:Rats, Inbred Strains; D015183:Restriction Mapping; D014158:Transcription, Genetic
D007527:Isoenzymes; D012333:RNA, Messenger; D000252:Calcium-Transporting ATPases