(620c) Complex Hyperthermophilic Proteases: the Effect of Beta Protein Content on Biochemical and Biophysical Properties of Proteasomes | AIChE

(620c) Complex Hyperthermophilic Proteases: the Effect of Beta Protein Content on Biochemical and Biophysical Properties of Proteasomes

Authors 

Michel, J. K. - Presenter, North Carolina State University
Madding, L. S. - Presenter, North Carolina State University
Shockley, K. R. - Presenter, North Carolina State University
Conners, S. B. - Presenter, North Carolina State University
Epting, K. L. - Presenter, North Carolina State University
Johnson, M. R. - Presenter, North Carolina State University
Tachdjian, S. - Presenter, North Carolina State University
Kelly, R. M. - Presenter, North Carolina State University


The genomes of hyperthermophilic microorganisms (growth Topt of at least 80°C) encode a variety of known and putative proteases with diverse structural features and biochemical properties. Recent use of genome sequence information, in conjunction with whole genome microarrays for model hyperthermophiles, has helped identify hyperthermophilic proteases, complemented information obtained from biochemical and biophysical studies, as well as providing clues to the physiological function of proteases in these microorganisms. In some cases, complex multimeric proteases have been shown to play an essential role in intracellular protein turnover under normal and stressed conditions in hyperthermophiles. For example, versions of the multicatalytic proteasome have been found in all hyperthermophilic archaea. In some cases, it appears from the molecular composition of proteasomes can be specifically adapted for biocatalysis. In eukaryotes, the composition of the proteasome core particle (CP or 20S proteasome) is based on as many different small alpha and beta type proteins (21-31 kDa) that assemble into heptameric stacked rings (α7, β7, β7, α7), creating multiple proteolytic specificities. Archaeal genomes typically encode only one or two versions of the proteasome alpha and beta protein elements, giving rise to much simpler proteasome assemblies. This comparatively simple situation, compared with eukaryotic proteasomes, facilitates efforts to understand the biochemical, biophysical and physiological significance of alpha and beta protein content.

The genomes of the hyperthermophilic archaea Pyrococcus furiosus and Sulfolobus solfataricus each encode one alpha but two beta proteasomal proteins. The relationship between proteasome protein composition, biocatalytic function and thermostability was examined for these two model organisms using functional genomics and proteomics tools. It was found that proteasome beta protein composition varies with respect to the in vivo and in vitro assembly temperature such that the biophysical and biochemical properties are tuned to environmental conditions. The significance of this aspect of proteasome structure and function will be discussed as will the consequences of this feature as it relates to physiological role and biotechnological uses. Also considered is how the proteasome fits into the proteolytic inventory in hyperthermophilic microorganisms.