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3.A.28. The AAA-ATPase, Bcs1 (Bcs1) Family

The mitochondrial AAA-ATPase, Bcs1, mediates topogenesis of the Rieske protein, Rip1, a component of respiratory chains in bacteria, mitochondria, and chloroplasts (Wagener et al. 2011). The oligomeric AAA-ATPase, Bcs1, is involved in export of the folded Fe-S domain of Rip1 across the inner membrane and insertion of its transmembrane segment into an assembly intermediate of the cytochrome bc1 complex. Structural elements in Rip1 are required for recognition and export by as well as ATP-dependent lateral release from the AAA-ATPase. In bacteria and chloroplasts, Rip1 uses the Tat machinery for topogenesis; however, mitochondria have lost this machinery during evolution, and a member of the AAA-ATPase family has taken over its function (Wagener et al., 2011).  Mutations in Bcs1 lead to different properties of the protein and different disease-related symptoms (Wagener and Neupert 2012).  A conserved α-helix in Bcs1 is required for Respiratory Complex III maturation (Sawamura et al. 2014). Human BCS1 has been implicated in human mitochondrial disorders (e.g. Björnstad and Gracile syndromes) (Ostojić et al. 2014). The outer membrane AAA-ATPase of Arabidopsis thaliana, AtOM66, affects cell death and pathogen resistance (Zhang et al. 2014).

References associated with 3.A.28 family:

Ostojić, J., J.P. Rago, and G. Dujardin. (2014). A novel mechanism involved in the coupling of mitochondrial biogenesis to oxidative phosphorylation. Microb Cell 1: 43-44. 28357209
Sawamura, R., T. Ogura, and M. Esaki. (2014). A conserved α helix of Bcs1, a mitochondrial AAA chaperone, is required for the Respiratory Complex III maturation. Biochem. Biophys. Res. Commun. 443: 997-1002. 24361883
Tamai, S., H. Iida, S. Yokota, T. Sayano, S. Kiguchiya, N. Ishihara, J. Hayashi, K. Mihara, and T. Oka. (2008). Characterization of the mitochondrial protein LETM1, which maintains the mitochondrial tubular shapes and interacts with the AAA-ATPase BCS1L. J Cell Sci 121: 2588-2600. 18628306
Wagener, N. and W. Neupert. (2012). Bcs1, a AAA protein of the mitochondria with a role in the biogenesis of the respiratory chain. J Struct Biol 179: 121-125. 22575765
Wagener, N., M. Ackermann, S. Funes, and W. Neupert. (2011). A pathway of protein translocation in mitochondria mediated by the AAA-ATPase Bcs1. Mol. Cell 44: 191-202. 22017868
Zhang, B., O. Van Aken, L. Thatcher, I. De Clercq, O. Duncan, S.R. Law, M.W. Murcha, M. van der Merwe, H.S. Seifi, C. Carrie, C. Cazzonelli, J. Radomiljac, M. Höfte, K.B. Singh, F. Van Breusegem, and J. Whelan. (2014). The mitochondrial outer membrane AAA ATPase AtOM66 affects cell death and pathogen resistance in Arabidopsis thaliana. Plant J. 80: 709-727. 25227923