A proteomic determination of cold adaptation in the Antarctic archaeon, Methanococcoides burtonii

Amber Goodchild, Neil F. W. Saunders, Haluk Ertan, Mark Raftery, Michael Guilhaus, Paul M. G. Curmi, Ricardo Cavicchioli

A global view of the biology of the cold-adapted archaeon Methanococcoides burtonii was achieved using proteomics. Proteins specific to growth at 4 degrees C versus T(opt) (23 degrees C) were identified by mass spectrometry using the draft genome sequence of M. burtonii. mRNA levels were determined for all genes identified by proteomics, and specific enzyme assays confirmed the protein expression results. Key aspects of cold adaptation related to transcription, protein folding and metabolism, including specific roles for RNA polymerase subunit E, a response regulator and peptidyl prolyl cis/trans isomerase. Heat shock protein DnaK was expressed during growth at T(opt), indicating that growth at 'optimal' temperatures was stressful for this cold-adapted organism. Expression of trimethylamine methyltransferase involves contiguous translation of two open reading frames, which is likely to result from incorporation of pyrrolysine at an amber stop codon. Thermal regulation in M. burtonii is achieved through complex gene expression events involving gene clusters and operons, through to protein modifications.