Tropomyosin: Difference between revisions

Tropomyosin, as mentioned above, will form a long polymer along the length of actin in a head-to-tail overlap<ref name="Frye"/>. This <scene name='User:Gregory_Hoeprich/Sandbox_1/Tropomyosin_overlap/2'>overlap region</scene> occurs as the amino acids from the <scene name='41/410306/Tropomyosin_overlap_c_d/1'>N-terminus</scene> of one dimer overlaps with the amino acids of the <scene name='User:Gregory_Hoeprich/Sandbox_1/Tropomyosin_overlap_a_b/3'>C-terminus</scene> of another dimer.  There are several <scene name='User:Gregory_Hoeprich/Sandbox_1/Tropomyosin_overlap_a_b_e_f/1'>intermolecular contacts</scene> in the overlap region, which consist of ionic, hydrophobic and non-polar interactions<ref name="Frye"/>.  (Note: many of the methionine residues interacting between the dimers are selenomethionine, which are used here to help solve the x-ray crystal structure.)  Interestingly, most of the variation seen among tropomyosin isoforms is in the overlap region, which will affect polymer formation along the actin filament<ref name="Frye"/>.  The actin binding sites on tropomyosin (protein-protein interactions) are currently not easily recognizable, but it is thought that a periodic repeat of seven consensus residues contribute to tropomyosin binding to actin<ref name="Gunning"/>.  The seven fold repeat is  a mix of charged and non-polar residues in the 2,3 and 6 positions (see helical wheel diagram above)<ref name="Gunning"/>.