Proteome Analysis of Sulfolobus solfataricus P2 Propanol Metabolism

Sulfolobus solfataricus P2 is able to metabolize n-propanol as the sole carbon source. An average n-propanol consumption rate of 9.7 and 3.3 mg/L/hr was detected using GC-MS analysis from S. solfataricus cultures grown in 0.40 and 0.16% w/v n-propanol, respectively. The detection of propionaldehyde, the key intermediate of n-propanol degradation, produced at a rate of 1.3 and 1.0 mg/L/hr in 0.40 and 0.16% w/v n-propanol cultures, further validated the ability of S. solfataricus to utilize n-propanol. The translational and transcriptional responses of S. solfataricus grown on n-propanol versus glucose were also investigated using quantitative RT−PCR and iTRAQ approaches. Approximately 257 proteins with ≥2 MS/MS spectra were identified and quantified via iTRAQ. The global quantitative proteome overview obtained showed significant up-regulation of acetyl-CoA synthetases, propionyl-CoA carboxylase, and methylmalonyl-CoA mutase enzymes. This led to the proposition that the propionyl-CoA formed from n-propanol degradation is catabolised into the citrate cycle (central metabolism) via succinyl-CoA intermediates. In contrast, evidence obtained from these analysis approaches and in vivo stable isotope labeling experiments, suggests that S. solfataricus is only capable of converting isopropyl alcohol to acetone (and vice versa) but lacks the ability to further metabolize these compounds. Keywords: Sulfolobus solfataricus P2 • iTRAQ • alcohol dehydrogenase • shotgun proteomics • alcohol metabolism • stable isotope labeling