Titin Structure & Function: Difference between revisions
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== Overall Structure == | |||
Titin is a polypeptide chain protein which is greater than 1µm in length and 3-4 nm in width. The protein molecule has a molecular weight of up to approximately 4 Mda. Titin is a multidomain structure that which is found to be composed of two types of domains similar to immunoglobulin (Ig) and fibronectin. There are approximately Ig and fibronectin domains present in titin, with also kinase domains close to the carboxyl terminus. These two types of domains are β-sandwiches of seven or eight strands that are made of about 100 residues. The carboxyl terminus is in the head region of a titin molecule. The structure also contains specialized binding sites and a putative elastic region, the PEVK domain, and there is a unique sequence region part of a titin molecule. The multidomain structure is evident by the interdomain periodicity seen in the structure. A titin molecule is half a sacromeres size with the four regions of the I-band,the A-band, the M-line and the Z-line. The I-band section of the titin is made up of only Ig domains and unique sequences with the Ig domains arranged in tandem. The A-band section is the largest part of the protein molecule with a highly conserved sequence. In the A-band section the Ig and fibronectin domains are set up in a long range pattern and are called the super repeats. There are two types of the Ig and fibronectin sets that are arranged in long range patterns, made from either seven and eleven domains. Located near the end of the A-band there are six copies of small super repeats, that which are 25-30 nm long. The M-line contains the overlapped carboxyl terminus regions of the titin molecule. The Z-line region is on the opposite end which has the overlapped amino terminal regions of a molecule from the neighboring sacromere. | |||