Résumé
A novel human‐voltage‐dependent‐calcium‐channel (VDCC) β subunit was isolated from a 9‐week‐old human total‐embryo cDNA library. Of the four genes encoding β‐subunit isoforms that have been identified in animal species, this isoform shares strong similarity with the rat and rabbit β
3
‐related gene product and is referred to here as Hβ
3
subunit. The Hβ
3
isoform is the second β subunit identified in human. Its open reading frame encodes a 482‐amino‐acid protein with a predicted molecular mass of 54.571 kDa. The Hβ
3
mRNA is expressed mostly in brain, smooth muscle and ovary. The gene for the human Hβ
3
was specifically localized on chromosome 12q13. The cloned Hβ
3
subunit was further expressed in
Xenopus
oocytes to demonstrate its ability to modulate VDCC activity.