Titin kinase

Codes for a serine/threonine kinase domain ( the titin kinase... 

Centner, T., Yano, J., and Kimura, E. (2001). Identification of muscle specific ring finger proteins as potential regulators of the titin kinase domain. J. Mol. Biol. 306, 717-726. 

Mayans, O., van der Ven, P. F., and Wilm, M. (1998). Structural basis for activation of the titin kinase domain during myofibrillogenesis. Nature 395, 863-869. 

Fig. 15.1. Schematic illustration of the muscle. The force generating unit is the sarcomere with a length of about 2 tm. Contraction is caused by the myosin and actin filaments. Titin spans the whole half-sarcomere, keeps the myosin filaments in place and provides the muscle with its passive elasticity. At the M-line, where titin is cross-linked, the titin kinase is integrated with its surrounding and globular Ig and Fn domains. This position is ideal to detect the imbalances between neighboring filaments...

Champagne, M.B. Edwards, K.A. Erickson, H.P. Kiehart, D.P. Drosophila stretchin-MLCK is a novel member of the titin/myosin light chain kinase family. J. Mol. Biol., 300, 759-777 (2000)... 

Under the electron microscope titin appears as a flexible beaded string 4 nm in diameter. Most of the molecule is made up of repetitive domains of two types. In human cardiac titin there are 132 folded domains that resemble type III fibronectin repeats and 112 immunoglobulin-like domains.98 In a "PEVK region," between residues 163 and 2174, 70% of the residues are Pro, Glu, Val, or Lys. The titin molecule may be organized as polyproline helices in this elastic region.1023 At the C terminus of titin 800 residues, including a Ser / Thr protein kinase domain, are found within the M-line. 

Yamasaki, R., Wu, Y., and McNabb, M. (2002). Protein kinase A phosphorylates titin s cardiac-specific N2B domain and reduces passive tension in rat cardiac myocytes. Circ. Res. 90, 1181-1188. 

The morphology of the M band in cardiac muscle can be correlated roughly with heartbeat frequency. In general, cardiac M bands give a five line pattern, in which the Ml-line is relatively much stronger than the other M-lines (Pask et al. 1994). Five proteins have been described to be locahsed specifically in the M-band the muscle isoform of creatine kinase, M-protein, myomesin, skelemin and titin. 

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