MOLECULAR-CLONING OF CDNA-ENCODING THE INFINITY-UNIT OF CNGC GENE FROM HUMAN FETAL HEART

Cyclic nucleotide-gated ion channels (CNGCs) play crucial roles in vis ual and olfactory signal transduction. As a first step to explore the presence of a CNGC gene in human heart, we cloned a human heart CNGC g ene. The sequence consists of 111 bp 5' non-coding region and a 2064 b p open reading frame which is followed by a 459 bp 3' non-coding regio n. The predicted protein consists of 688 amino acids with a short high ly charged segment rich in lysine and glutamate. Sequence comparison i ndicates that the human heart cDNA is almost identical to the retinal rod photo receptor CNGC cDNA. However, the human cardiac cDNA is lacki ng a 205bp Alu fragment in the 5'-uncoding region, has a glutamic acid residue at amino acid position 129, and has a replacement of glutamic acid with a lysine residue at amino acid position 99. Data obtained w ith northern blot analysis confirm the presence of RNA for the CNGC al pha chain. This channel might play a role in cyclic nucleotide-mediate d cellular processes, such as the inotropic effect in the heart.