Cardiac troponin T forms a tetramer in vitro.
Cardiac troponin T (cTnT) is a myofibrillar protein essential for calcium-dependent contraction. This property has led to functional studies of developmentally expressed cTnT isoforms and mutants identified in patients with hypertrophic cardiomyopathy. The release of cTnT into the serum following myocardial infarction has led to the development of antibody-based assays for measuring cTnT serum concentration. We examined the behavior of cTnT in solution. Recombinant human cTnT3, the dominant isoform in the adult human heart, was used. The protein was pure and functional, as demonstrated by SDS-PAGE and surface plasmon resonance. cTnT3 was found to bind specifically and in a concentration-dependent manner to cTnC. Routine size exclusion chromatography suggested a higher-than-expected MW for cTnT. Using analytical ultracentrifugation, we found cTnT3 in solution to be mainly in the form of a tightly bound tetramer at concentrations as low as 4 micromol/L. Our sedimentation velocity and transmission electron microscopy results indicate that the tetramer's shape is elongated rather than globular. CTnT's self-association in solution is an important consideration in the design and interpretation of experiments with the aim of understanding the biochemical and biophysical properties of cTnT, its isoforms, and its mutants.
Lounes
Karim C
KC
Department of Pediatrics, Duke University Medical Center, Durham, North Carolina 27710, USA.
Demeler
Borries
B
Anderson
David E
DE
Gomes
Aldrin W
AW
Potter
James D
JD
Nassar
Rashid
R
Anderson
Page A W
PA
D001704:Biopolymers / Q000737:chemistry*; D007700:Kinetics; D008854:Microscopy, Electron; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D020107:Troponin T / Q000737:chemistry*; D014461:Ultracentrifugation
D001704:Biopolymers; D011994:Recombinant Proteins; D020107:Troponin T