Shape and flexibility in the titin 11-domain super-repeat.
Titin is a giant protein of striated muscle with important roles in the assembly, intracellular signalling and passive mechanical properties of sarcomeres. The molecule consists principally of approximately 300 immunoglobulin and fibronectin domains arranged in a chain more than 1 mum long. The isoform-dependent N-terminal part of the molecule forms an elastic connection between the end of the thick filament and the Z-line. The larger, constitutively expressed C-terminal part is bound to the thick filament. Through most of the thick filament part, the immunoglobulin and fibronectin domains are arranged in a repeating pattern of 11 domains termed the 'large super-repeat'. There are 11 contiguous copies of the large super-repeat making up a segment of the molecule nearly 0.5 mum long. We have studied a set of two-domain and three-domain recombinant fragments from the large super-repeat region by electron microscopy, synchrotron X-ray solution scattering and analytical ultracentrifugation, with the goal of reconstructing the overall structure of this part of titin. The data illustrate different average conformations in different domain pairs, which correlate with differences in interdomain linker lengths. They also illustrate interdomain bending and flexibility around average conformations. Overall, the data favour a helical conformation in the super-repeat. They also suggest that this region of titin is dimerized when bound to the thick filament.
Institute for Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK. l.tskhovrebova@leeds.ac.uk
Larissa
L
Tskhovrebova
Matt L
ML
Walker
J Günter
JG
Grossmann
G Nasir
GN
Khan
Andy
A
Baron
John
J
Trinick
D064211:Connectin; D019281:Dimerization; D008854:Microscopy, Electron; D008958:Models, Molecular; D009124:Muscle Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D011487:Protein Conformation; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D053838:Scattering, Small Angle; D014461:Ultracentrifugation
D064211:Connectin; D009124:Muscle Proteins; D011494:Protein Kinases