Subsystem: Cluster-based Subsystem Grouping Hypotheticals - perhaps Proteosome Related

This subsystem's description is:

This is a cluster-based subsystem relating to the proteosome (I believe).

The twin-arginine translocation (Tat) systems transport folded proteins across the plasma membrane. TatA and TatC are part of this cluster.
Pup ligase pafA is also part:

Biol Direct. 2008 Nov 3;3:45.
Unraveling the biochemistry and provenance of pupylation: a prokaryotic analog of ubiquitination.
Iyer LM, Burroughs AM, Aravind L.

National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA.

Recently Mycobacterium tuberculosis was shown to possess a novel protein modification, in which a small protein Pup is conjugated to the epsilon-amino groups of lysines in target proteins. Analogous to ubiquitin modification in eukaryotes, this remarkable modification recruits proteins for degradation via archaeal-type proteasomes found in mycobacteria and allied actinobacteria. While a mycobacterial protein named PafA was found to be required for this conjugation reaction, its biochemical mechanism has not been elucidated. Using sensitive sequence profile comparison methods we establish that the PafA family proteins are related to the gamma-glutamyl-cysteine synthetase and glutamine synthetase. Hence, we predict that PafA is the Pup ligase, which catalyzes the ATP-dependent ligation of the terminal gamma-carboxylate of glutamate to lysines, similar to the above enzymes. We further discovered that an ortholog of the eukaryotic PAC2 (e.g. cg2106) is often present in the vicinity of the actinobacterial Pup-proteasome gene neighborhoods and is likely to represent the ancestral proteasomal chaperone. Pup-conjugation is sporadically present outside the actinobacteria in certain lineages, such as verrucomicrobia, nitrospirae, deltaproteobacteria and planctomycetes, and in the latter two lineages it might modify membrane proteins. Reviewers: This article was reviewed by M. Madan Babu and Andrei Osterman.

PMID: 18980670

Science. 2008 Nov 14;322(5904):1104-7. Epub 2008 Oct 2.

Comment in:
Science. 2008 Nov 14;322(5904):1062-3.

Ubiquitin-like protein involved in the proteasome pathway of Mycobacterium tuberculosis.
Pearce MJ, Mintseris J, Ferreyra J, Gygi SP, Darwin KH.

Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA.

The protein modifier ubiquitin is a signal for proteasome-mediated degradation in eukaryotes. Proteasome-bearing prokaryotes have been thought to degrade proteins via a ubiquitin-independent pathway. We have identified a prokaryotic ubiquitin-like protein, Pup (Rv2111c), which was specifically conjugated to proteasome substrates in the pathogen Mycobacterium tuberculosis. Pupylation occurred on lysines and required proteasome accessory factor A (PafA). In a pafA mutant, pupylated proteins were absent and substrates accumulated, thereby connecting pupylation with degradation. Although analogous to ubiquitylation, pupylation appears to proceed by a different chemistry. Thus, like eukaryotes, bacteria may use a small-protein modifier to control protein stability.

PMID: 18832610

For more information, please check out the description and the additional notes tabs, below

DiagramFunctional RolesSubsystem SpreadsheetDescription 

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Group Alias
Abbrev.Functional RoleReactionsScenario ReactionsGOLiterature

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