Titin Structure & Function: Difference between revisions

Titin is a polypeptide chain protein which is greater than 1µm in length and 3-4 nm in width <ref name=journal1>PMID:14506471</ref>. 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.<ref name=journal2/>  There are approximately Ig and fibronectin domains present in titin, with also kinase domains close to the carboxyl terminus.<ref name=journal1/>  These two types of domains are β-sandwiches of seven or eight strands that are made of about 100 residues.<ref name=journal1/>  The carboxyl terminus is in the head region of a titin molecule, the <scene name='Sandbox_183/N_to_c_terminus/2'>carboxyl terminus </scene>is represented as the red part molecule image.<ref name=journal1/>  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 <ref name=journal2>PMID:9153398</ref>.  The multidomain structure is evident by the interdomain periodicity seen in the structure.<ref name=journal1/>  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. <ref name=journal1/>  The I-band section of the titin is made up of only Ig domains and unique sequences with the Ig domains arranged in tandem.<ref name=journal1/> The A-band section is the largest part of the protein molecule with a highly conserved sequence.<ref name=journal1/>  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. <ref name=journal1/> The M-line contains the overlapped carboxyl terminus regions of the titin molecule. <ref name=journal1/>  The Z-line region is on the opposite end which has the overlapped amino terminal regions of a molecule from the neighboring sacromere.<ref name=journal1/>