Crystal Structure of Mycobacterium tuberculosis SecA, a Preprotein Translocating ATPase

• Published in: Proceedings of the National Academy of Sciences - PNAS 2003-03, Vol.100 (5), p.2243-2248
• Main Authors: Sharma, Vivek, Arockiasamy, Arulandu, Ronning, Donald R., Savva, Christos G., Holzenburg, Andreas, Braunstein, Miriam, Jacobs, William R., Sacchettini, James C.
• Format: Article
• Language: English
• Subjects: Adenosine Diphosphate - metabolism; Adenosine triphosphatases; Adenosine Triphosphatases - chemistry; Adenosine Triphosphate - metabolism; Bacteria; Bacterial Proteins; Binding Sites; Biological Sciences; Cell membranes; Cloning, Molecular; Crystal structure; Crystallography; Crystallography, X-Ray; Cytoplasm - metabolism; Dimerization; Dimers; Electron density; Electrons; Escherichia coli Proteins - chemistry; Hydrolysis; Membrane Transport Proteins - chemistry; Models, Molecular; Molecules; Mycobacterium tuberculosis - enzymology; Neurotransmitters; Nucleotides; Protein Structure, Secondary; Protein Structure, Tertiary; Protein Transport; Proteins; SEC Translocation Channels; SecA Proteins; Tuberculosis
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0538077100

In bacteria, the majority of exported proteins are translocated by the Sec system, which recognizes the signal sequence of a preprotein and uses ATP and the proton motive force to mediate protein translocation across the cytoplasmic membrane. SecA is an essential protein component of this system, containing the molecular motor that facilitates translocation. Here we report the three-dimensional structure of the SecA protein of Mycobacterium tuberculosis. Each subunit of the homodimer contains a "motor" domain and a translocation domain. The structure predicts that SecA can interact with the SecYEG pore and function as a molecular ratchet that uses ATP hydrolysis for physical movement of the preprotein. Knowledge of this structure provides a framework for further elucidation of the translocation process.