Chaperonins from an Antarctic archaeon are predominantly monomeric: crystal structure of an open state monomer
Article first published online: 7 APR 2011
© 2011 Society for Applied Microbiology and Blackwell Publishing Ltd
Thematic Issue: Extremophiles. Guest Editors: Ricardo Cavicchioli, Ricardo Amils, Dirk Wagner, Terry McGenity
Volume 13, Issue 8, pages 2232–2249, August 2011
How to Cite
Pilak, O., Harrop, S. J., Siddiqui, K. S., Chong, K., De Francisci, D., Burg, D., Williams, T. J., Cavicchioli, R. and Curmi, P. M. G. (2011), Chaperonins from an Antarctic archaeon are predominantly monomeric: crystal structure of an open state monomer. Environmental Microbiology, 13: 2232–2249. doi: 10.1111/j.1462-2920.2011.02477.x
- Issue published online: 21 AUG 2011
- Article first published online: 7 APR 2011
- Received 24 November, 2010; accepted 26 February, 2011.
Archaea are abundant in permanently cold environments. The Antarctic methanogen, Methanococcoides burtonii, has proven an excellent model for studying molecular mechanisms of cold adaptation. Methanococcoides burtonii contains three group II chaperonins that diverged prior to its closest orthologues from mesophilic Methanosarcina spp. The relative abundance of the three chaperonins shows little dependence on organism growth temperature, except at the highest temperatures, where the most thermally stable chaperonin increases in abundance. In vitro and in vivo, the M. burtonii chaperonins are predominantly monomeric, with only 23–33% oligomeric, thereby differing from other archaea where an oligomeric ring form is dominant. The crystal structure of an N-terminally truncated chaperonin reveals a monomeric protein with a fully open nucleotide binding site. When compared with closed state group II chaperonin structures, a large-scale ∼30° rotation between the equatorial and intermediate domains is observed resulting in an open nucleotide binding site. This is analogous to the transition observed between open and closed states of group I chaperonins but contrasts with recent archaeal group II chaperonin open state ring structures. The predominance of monomeric form and the ability to adopt a fully open nucleotide site appear to be unique features of the M. burtonii group II chaperonins.