Molecular cloning and characterization of mouse cardiac triadin isoforms

Triadin is a ryanodine receptor and calsequestrin binding protein located i n junctional sarcoplasmic reticulum of striated muscles. In the present stu dy, mouse cardiac triadin cDNAs have been identified by cDNA library screen ing and RT-PCR. The deduced as sequences show that the three isoforms consi st of 277, 293 and 305 as giving rise to the molecular weights of approxima tely 31,414, 33,066, and 34,328, respectively. The isoforms have identical 262 as N-terminal sequences, whereas they have distinct C-terminal sequence s. Northern blot analysis using a cDNA probe representing the N-terminal co mmon region of triadin revealed that the mouse triadins were present both i n heart and skeletal muscles. The estimated sizes of the transcripts were a pproximately 1.3, 4.3 and 5 kb in heart and 5, 5.5 and 7 kb in skeletal mus cle. Endo H treatment and Western blot analysis of isolated mouse cardiac s arcoplasmic reticulum and in vitro translation products indicate that there are three distinct mouse cardiac triadin isoforms having molecular weights of 35, 35.5 and 40 kDa. We termed those three isoforms as mouse cardiac tr iadin 1, mouse cardiac triadin 2 and mouse cardiac triadin 3. (C) 2001 Else vier Science B.V. All rights reserved.