Evidence for two isoforms of the endoplasmic-reticulum Ca2+ pump in pig smooth muscle.
cDNA clones coding for the endoplasmic reticulum Ca2+-transport ATPase have been cloned from a pig smooth-muscle cDNA library. The transcripts can be divided into two classes which differ in their 3' ends due to alternative splicing of the primary gene transcript. The class 1 cDNA encodes a protein of 997 amino acids (Mr 110,000). The class 2 protein (1042 amino acids; Mr 115,000) is completely identical to the class 1 protein except that the four C-terminal amino acids of the class 1 protein are replaced in the class 2 protein with a tail of 49 amino acids. Comparison of these sequences with other Ca2+ pump sequences reveals that the class 1 isoform corresponds to the sarcoplasmic reticulum Ca2+ pump of slow-twitch skeletal/cardiac muscle, whereas the class 2 protein corresponds to a Ca2+ pump recently detected in non-muscle tissues.
Eggermont
J A
JA
Laboratorium voor Fysiologie, Leuven, Belgium.
Wuytack
F
F
De Jaegere
S
S
Nelles
L
L
Casteels
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D000252:Calcium-Transporting ATPases; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D007527:Isoenzymes; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000201:enzymology* / Q000648:ultrastructure; D013552:Swine
D007527:Isoenzymes; D000252:Calcium-Transporting ATPases