Structural Basis of Pilus Subunit Recognition by the PaPd Chaperone

Based primarily on 16S rRNA sequence comparisons, life has been broadly divided into the three domains of Bacteria, Archaea, and Eukarya. Archaea is further classified into Crenarchaea and Euryarchaea. Archaea generally thrive in extreme environments as assessed by temperature, pH, and salinity. For many prokaryotic organisms, ribosomal proteins (RP), transcription͞translation factors, and chaperone genes tend to be highly expressed. A gene is predicted highly expressed (PHX) if its codon usage is rather similar to the average codon usage of at least one of the RP, transcription͞ translation factors, and chaperone gene classes and deviates strongly from the average gene of the genome. The thermosome (Ths) chaperonin family represents the most salient PHX genes among Archaea. The chaperones Trigger factor and HSP70 have overlapping functions in the folding process, but both of these proteins are lacking in most archaea where they may be substituted by the chaperone prefoldin. Other distinctive PHX proteins of Archaea, absent from Bacteria, include the proliferating cell nuclear antigen PCNA, a replication auxiliary factor responsible for tethering the catalytic unit of DNA polymerase to DNA during highspeed replication, and the acidic RP P0, which helps to initiate mRNA translation at the ribosome. Other PHX genes feature Cell division control protein 48 (Cdc48), whereas the bacterial septation proteins FtsZ and minD are lacking in Crenarchaea. RadA is a major DNA repair and recombination protein of Archaea. Archaeal genomes feature a strong Shine-Dalgarno ribosome-binding motif more pronounced in Euryarchaea compared with Crenarchaea.acidic ribosomal proteins ͉ Archaea ͉ highly expressed proteins ͉ thermosome T he identity of the three domains of life (1) and their relationships are controversial (2-11). Archaea form a heterogeneous clade composed of a mosaic of bacterial, eukaryotic, and unique features. Archaea and Eukarya share many homologous genes involved in information processing (replication, transcription, and translation), whereas Archaea and Bacteria share many morphological structures and metabolic proteins (10, 12). Of 19 archaeal genomes completely sequenced (Table 1, mid-2004), 4 are from Crenarchaea and 14 are from Euryarchaea. Nanoarchaeum equitans, a parasitic archaeon that lives in coculture with the archaeon Ignicoccus, has been tentatively assigned to the separate group of Nanoarchaea. Most sequenced archaea, to date, are thermophilic, generally prefer extreme environments, and are found in most ecosystems. The four sequenced crenarchaea are all hyperthermophiles (optimal growth temperature, Ն75°C), although mesophilic crenarchaea have been putatively found in pelagic waters (3, 13). Among the Euryarchaea, six are methanogens, including three mesophiles, Methanosarcina acetivorans, Methanosarcina mazei, and Methanococcus maripaludis. Halobacterium NRC-1 is also mesophilic, thriving in high salt concentrations. Most sequenced archaea, excluding methanogens (lifestyle strictly anaerobic, meta...

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“…Specialized complex structures in cells often need their own ''dedicated'' chaperones (e.g., ref. 49).…”

Section: Resultsmentioning

confidence: 99%

Predicted highly expressed genes in archaeal genomes

Karlin

Mrázek

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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“…Another key binding motif, first identified in the complex between the PapD chaperone and a C-terminal peptide of the subunit PapG 40 , is the C-terminal F strand of the pilin domain. This F strandchaperone interaction is also conserved in all structures of FimCsubunit complexes 1,25,26 .…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the carboxyl group of the C-terminal Gln159 forms two salt bridges with Arg8 and Lys112, two invariant residues located in the interdomain cleft of the chaperone. Mutations of the corresponding residues studied in PapD, a close homolog of FimC, revealed that both residues are critical for pilus subunit binding 40 . The N-terminal region of FimA t , including the A′ strand, interacts with residues 1-7 of FimC, whereas the A′ strand forms an antiparallel β-sheet with the G strand of FimC.…”

Section: Fimc-fima T Structurementioning

confidence: 99%

Quality control of disulfide bond formation in pilus subunits by the chaperone FimC

et al. 2012

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“…The PapG adhesin is degraded in the periplasm, if expressed in the absence of PapD [6]. Co-expression of the chaperone stabilizes the adhesin in a native-like conformation in a PapD^PapG periplasmic complex.…”

Section: Binding Of P Pili and Papd^papg Adhesin Complex To Mvm And Slpmentioning

confidence: 99%

“…The assembly of P pili requires the PapD immunoglobulin-like chaperone, which binds nascently translocated subunits via a L-zipper recognition paradigm. This interaction facilitates the release of subunits from the cytoplasmic membrane as soluble periplasmic chaperoneŝ ubunit complexes [5,6]. The chaperone^subunit complexes are then escorted to outer membrane assembly sites comprised of PapC where the complexes are dissociated and the subunits are incorporated into pili across the outer membrane [7].…”

Section: Introductionmentioning

confidence: 99%