Quantitative proteomics of the archaeon Methanococcus maripaludis validated by microarray analysis and real time PCR

Area of Science:

• Microbiology
• Proteomics
• Genomics

Background:

• Methanococcus maripaludis is a model organism for hydrogenotrophic methanogens.
• Accurate quantification of protein expression is crucial for understanding cellular processes.

Purpose of the Study:

• To validate quantitative protein expression ratios on a proteome-wide scale in M. maripaludis.
• To compare global protein and mRNA levels between wild-type and mutant strains.

Main Methods:

• Quantitative multidimensional capillary HPLC and quadrupole ion trap mass spectrometry for proteomics.
• Spotted cDNA arrays for transcriptomics.
• Linear regression and outlier detection methods for data analysis.

Main Results:

• Proteomics covered 55% of the genome, detecting 939 proteins.
• Correlation between proteomic and microarray expression ratios was 0.24, improving to 0.61 for significantly changed genes.
• 15 ORFs showed overexpression by both methods; 2 showed conflicting results.

Conclusions:

• Quantitative proteomics provides a valuable tool for validating gene expression in archaea.
• Discrepancies between protein and mRNA levels highlight post-transcriptional regulation.
• The study advances the understanding of gene expression in M. maripaludis.