2K8X

GlyTM1b(1-19)zip: A Chimeric Peptide Model of the N-Terminus of a Rat Short Alpha-Tropomyosin with the N-Terminus Encoded by Exon 1b in Complex with TM9d(252-284), a Peptide Model Containing the C Terminus of Alpha-Tropomyosin Encoded by Exon 9d

Summary for 2K8X

• Entry DOI: 10.2210/pdb2k8x/pdb
• Related: 1IHQ
• NMR Information: BMRB: 15965
• Descriptor: TM1b(1-19)Zip (1 entity in total)
• Functional Keywords: tropomyosin, n terminus, protein complex, c terminus, tropomodulin binding protein, overlap complex, coiled coil, cytoskeletal regulatory protein, actin-binding protein
• Biological source: Rattus norvegicus (rat)
• Total number of polymer chains: 2
• Total formula weight: 8663.83

Authors

Greenfield, N.J.,Kotylanskaya, L.,Hitchcock-DeGregori, S.E. (deposition date: 2008-09-25, release date: 2009-04-28, Last modification date: 2024-05-22)

Primary citation

Greenfield, N.J.,Kotlyanskaya, L.,Hitchcock-DeGregori, S.E.
Structure of the N terminus of a nonmuscle alpha-tropomyosin in complex with the C terminus: implications for actin binding.
Biochemistry, 48:1272-1283, 2009

PubMed Abstract: Tropomyosin is a coiled-coil actin binding protein that stabilizes the filament, protects it from severing, and cooperatively regulates actin's interaction with myosin. Depending on the first coding exon, tropomyosins are low molecular weight (LMW), found in the cytoskeleton and predominant in transformed cells, or high molecular weight (HMW), found in muscle and nonmuscle cells. The N- and C-terminal ends form a complex that allows tropomyosin to associate N terminus-to-C terminus along the actin filament. We determined the structure of a LMW tropomyosin N-terminal model peptide complexed with a smooth/nonmuscle tropomyosin C-terminal peptide. Using NMR and circular dichroism we showed that both ends become more helical upon complex formation but that the C-terminal peptide is partially unfolded at 20 degrees C. The first five residues of the N terminus that are disordered in the free peptide are more helical and are part of the overlap complex. NMR data indicate residues 2-17 bind to the C terminus in the complex. The data support a model for the LMW overlap complex that is homologous to the striated muscle tropomyosin complex in which the ends are oriented in parallel N terminus-to-C terminus with the plane of the N-terminal coiled coil perpendicular to the plane of the C terminus. The main difference is that the overlap spans 16 residues in the LMW tropomyosin complex compared to 11 residues in the HMW striated muscle overlap complex. We discuss the relevance of a stable but dynamic intermolecular junction for high-affinity binding to actin.

PubMed: 19170537
DOI: 10.1021/bi801861k

Experimental method

SOLUTION NMR