Proteolysis in hyperthermophilic microorganisms

Abstract

Proteases are found in every cell, where they recognize and break down unneeded or abnormal polypeptides or peptide-based nutrients within or outside the cell. Genome sequence data can be used to compare proteolytic enzyme inventories of different organisms as they relate to physiological needs for protein modification and hydrolysis. In this review, we exploit genome sequence data to compare hyperthermophilic microorganisms from the euryarchaeotal genus Pyrococcus, the crenarchaeote Sulfolobus solfataricus, and the bacterium Thermotoga maritima. An overview of the proteases in these organisms is given based on those proteases that have been characterized and on putative proteases that have been identified from genomic sequences, but have yet to be characterized. The analysis revealed both similarities and differences in the mechanisms utilized for proteolysis by each of these hyperthermophiles and indicated how these mechanisms relate to proteolysis in less thermophilic cells and organisms.

Proteolytic inventory of Thermococcus kodakaraensis

“…It is also considered that membrane bound Lon Tk protease might have replaced FtsH, another important ATP dependent membrane bound peptidase which is absent in archaea (Ward et al, 2002). We have noticed that Nand C-terminal of Lon Tk are quite similar with the other members of the order Thermococcales.…”

“…The genome sequence of T. kodakaraensis has revealed the presence of an open reading frame having homology with α subunit and two with β subunits of proteasome indicating the presence of a proteasome complex consisting of one α and two different types of β subunits similar to other hyperthermophilc archaea (Ward et al, 2002).…”

“…It was first reported by Dahlmann and co-workers (Dahlmann et al, 1985) as "multicatalytic proteinase" and then named "proteasome" (Arrigo et al, 1988). It is ubiquitously present in eukaryotes and archaea whereas, there is no report for its existence in bacteria except for the gram-positive actinomycetes (Ward et al, 2002). Eukaryotes have 26S proteasome complex while in archaea it is 20S complex.…”

“…Another intracellular peptidase from P. horikoshii (Php I) has been characterized. Its three dimensional structure revealed that it exists in dodecameric form having two identical six membered rings, each with axes of symmetry such that it consists of a dimer of trimers or trimer of dimers (Ward et al, 2002).…”

Purification and Characterization of an Intracellular Chymotrypsin-Like Serine Protease fromThermoplasma volcanium

“…[11][12][13] Genome sequence data revealed even more expansive proteolytic genotypes of these organisms than can be inferred from biochemical analyses. 14) A majority of these organisms are capable of growth on proteinaceous substrates. 15,16) Therefore, the SP enzyme family in archaea might be involved in generating a pool of intracellular peptides and amino acids.…”