Structure of a tropomyosin N-terminal fragment at 0.98 Å resolution

Abstract

Tropomyosin (TM) is an elongated two-chain protein that binds along actin filaments. Important binding sites are localized in the N-terminus of tropo-myosin. The structure of the N-terminus of the long muscle α-TM has been solved by both NMR and X-ray crystallography. Only the NMR structure of the N-terminus of the short nonmuscle α-TM is available. Here, the crystal structure of the N-terminus of the short nonmuscle α-TM (αTm1bZip) at a resolution of 0.98 Å is reported, which was solved from crystals belonging to space group P3 1 with unit-cell parameters a = b = 33.00, c = 52.03 Å, α= Β = 90, γ= 120°. The first five N-terminal residues are flexible and residues 6-35 form an-helical coiled coil. The overall fold and the secondary structure of the crystal structure of αTM1bZip are highly similar to the NMR structure and the atomic coordinates of the corresponding C α atoms between the two structures superimpose with a root-mean-square deviation of 0.60 Å. The crystal structure validates the NMR structure, with the positions of the side chains being determined precisely in our structure. © 2011 International Union of Crystallography Printed in Singapore - all rights reserved.