The proteome of Mycoplasma genitalium - Chaps-soluble component

Mycoplasma genitalium is the smallest member of the class Mollicutes, with a genome size of 580 kb. It has the potential to express 480 gene products, and is therefore considered to be an excellent model to assess: (a) the mi nimum metabolism required by a free living cell; and (b) proteomic technolo gies and the information obtained by proteome analysis. Here, we report on the most complete proteome observed at 73% (expected proteome), and analyse d at 33% (reported proteome). The use of four overlapping pH windows in con junction with SDS/PAGE has allowed 427 distinct proteins to be resolved in association with the exponential growth of M. genitalium. Proof of expressi on for 201 proteins of sufficient abundance on silver stained two-dimension al gels was obtained using peptide mass fingerprinting (PMF) of which 158 w ere identified. The potential for gene product modification in even the sim plest known self-replicating organism was quantified at a ratio of 1.22 : 1 , more proteins than genes. A reduction in protein expression of 42% was ob served for post-exponentially-grown cells. DnaK, GroEL, DNA gyrase, and a c ytadherence accessory protein were significantly elevated, while some ribos omal proteins were reduced in relative abundance. The strengths and weaknes ses of techniques employed were assessed with respect to the observed and p redicted proteome derived from DNA sequence information. Proteomics was sho wn to provide a perspective into the biochemical and metabolic activities o f this organism, beyond that obtainable by sequencing alone.