Growth Kinetics of Extremely Halophilic
            <i>Archaea</i>
            (Family
            <i>Halobacteriaceae</i>
            ) as Revealed by Arrhenius Plots

Robinson, Jessie L.; Pyzyna, Brandy; Atrasz, Rachelle G.; Henderson, Christine; Morrill, Kira L.; Burd, Anna Mae; DeSoucy, Erik S.; Fogleman, Rex E.; Naylor, John; Steele, Sarah M.; Elliott, David K.; Leyva, Kathryn J.; Shand, Richard F.

doi:10.1128/jb.187.3.923-929.2005

Cited by 95 publications

(75 citation statements)

References 24 publications

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“…It should also be noted that growth at 50°C of the ⌬psmA strain expressing psmA-His 6 (␣1) in trans [GZ130(pJAM204)] was comparable to that of H26, the parent strain of this study (data not shown). Likewise, the Arrhenius plot for cells expressing wild-type ␣1 in this study is in good agreement with that previously published for growth of H. volcanii DS70 (38). It is surprising that such a dramatic increase in overall growth rate, cell yield, and tolerance of stress (low salt and high temperature) was observed for the ␣1 Q2T variant compared to the wild type, since the difference between the two strains expressing these variants at the genetic level is only two nucleotide substitutions in the penultimate codon of the 5Ј end of the psmA gene resulting in a single-amino-acid substitution.…”

supporting

confidence: 81%

The N-Terminal Penultimate Residue of 20S Proteasome α1 Influences its N ^α Acetylation and Protein Levels as Well as Growth Rate and Stress Responses of Haloferax volcanii

2009

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Proteasomes are energy-dependent proteolytic machines. We elaborate here on the previously observed N ␣ acetylation of the initiator methionine of the ␣1 protein of 20S core particles (CPs) of Haloferax volcanii proteasomes. Quantitative mass spectrometry revealed this was the dominant N-terminal form of ␣1 in H. volcanii cells. To further examine this, ␣1 proteins with substitutions in the N-terminal penultimate residue as well as deletion of the CP "gate" formed by the ␣1 N terminus were examined for their N ␣ acetylation. Both the "gate" deletion and Q2A substitution completely altered the N ␣ -acetylation pattern of ␣1, with the deletion rendering ␣1 unavailable for N ␣ acetylation and the Q2A modification apparently enhancing cleavage of ␣1 by methionine aminopeptidase (MAP), resulting in acetylation of the N-terminal alanine. Cells expressing these two ␣1 variants were less tolerant of hypoosmotic stress than the wild type and produced CPs with enhanced peptidase activity. Although ␣1 proteins with Q2D, Q2P, and Q2T substitutions were N ␣ acetylated in CPs similar to the wild type, cells expressing these variants accumulated unusually high levels of ␣1 as rings in N ␣ -acetylated, unmodified, and/or MAP-cleaved forms. More detailed examination of this group revealed that while CP peptidase activity was not impaired, cells expressing these ␣1 variants displayed higher growth rates and were more tolerant of hypoosmotic and high-temperature stress than the wild type. Overall, these results suggest that N ␣ acetylation of ␣1 is important in CP assembly and activity, high levels of ␣1 rings enhance cell proliferation and stress tolerance, and unregulated opening of the CP "gate" impairs the ability of cells to overcome salt stress.Proteolysis is important in regulation and protein quality control. Energy-dependent proteases are crucial to early stages of these proteolytic events and include proteasomes, multicatalytic proteases present in all eukaryotes and archaea and in some bacteria. The catalytic component of proteasomes, the 20S core particle (CP), consists of four heptameric rings of ␣-and ␤-type subunits stacked as a barrel in an ␣7␤7␤7␣7 configuration and is essential for growth of archaeal and eukaryotic cells (39, 54). The active sites responsible for peptide bond hydrolysis are formed by N-terminal Thr residues of ␤-type subunits and are sequestered within the central chamber of the barrel-like structure. Energy-dependent triple-A ATPases, including regulatory particle triple-A ATPases (Rpt) in eukaryotes and proteasome-activating nucleotidases (PAN) in archaea, mediate the unfolding and translocation of substrate proteins through the ␣-rings for degradation within the CP (39, 40).One major difference between eukaryotic and prokaryotic proteasomal CPs is in the crystal structure of the channel opening formed by the ␣-rings. Due to partial disorder of the ␣-subunit N termini, the site of substrate entry appears open at the ends of the cylinders of archaeal and bacterial CPs (e.g., CPs of Thermoplasma ...

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supporting

confidence: 81%

The N-Terminal Penultimate Residue of 20S Proteasome α1 Influences its N ^α Acetylation and Protein Levels as Well as Growth Rate and Stress Responses of Haloferax volcanii

2009

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“…Haloferax volcanii strain DS70 (Wendoloski et al, 2001) was grown with shaking (180 r.p.m.) at 45 uC (Robinson et al, 2005) and cultured in a medium containing (l 21 ) 125 g (2.1 M or 12 %, optimal salinity) or 206 g (3.5 M or 20 %, high, non-optimal salinity) NaCl, 45 g MgCl 2 . 6H 2 O, 10 g MgSO 4 .…”

Section: Methodsmentioning

confidence: 99%

Proteomic analysis of Haloferax volcanii reveals salinity-mediated regulation of the stress response protein PspA

et al. 2008

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A proteomic survey of the halophilic archaeon Haloferax volcanii was performed by comparative two-dimensional gel electrophoresis in order to determine the molecular effects of salt stress on the organism. Cells were grown under optimal (2.1 M) and high (3.5 M) NaCl conditions. From this analysis, over 44 protein spots responsive to these conditions were detected. These spots were excised, digested in-gel with trypsin, subjected to QSTAR tandem mass spectrometry (LC/MS/MS) analysis, and identified by comparing the MS/MS-derived peptide sequence to that deduced from the H. volcanii genome. Approximately 40 % of the proteins detected (18 in total) displayed differential abundance based on the detection of at least two peptide fragments per protein and overall MOWSE scores of ¢75 per protein. All of these identified proteins were either uniquely present or 2.3-to 26-fold higher in abundance under one condition compared to the other. The majority of proteins identified in this study were preferentially displayed under optimal salinity and primarily involved in translation, transport and metabolism. However, one protein of interest whose transcript levels were confirmed in these studies to be upregulated under high salt conditions was identified as a homologue of the phage shock protein PspA. The pspA gene belongs to the psp stress-responsive regulon commonly found among Gram-negative bacteria where its transcription is stimulated by a wide variety of stressors, including heat shock, osmotic shock and prolonged stationary-phase incubation. Homologues of PspA are also found among the genomes of cyanobacteria, higher plants and other Archaea, suggesting that this protein may retain some aspects of functional conservation across the three domains of life. Given its integral role in sensing a variety of membrane stressors in bacteria, these results suggest that PspA may play an important role in hypersaline adaptation in H. volcanii.

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“…To investigate whether UbaA, SAMP, and other SAMP-associated proteins are needed for optimal growth at high temperature, the aerobic growth of H. volcanii parent and single knockout strains was monitored on rich medium at temperatures equal to and above the 42 to 45°C optimum (28). Although all strains grew similar to wild-type at 42°C, ubaA and samp2 mutants were retarded in growth at 50°C (SI Appendix, Fig.…”

Section: Ubaa and Samp2 Are Needed For Optimal Growth At Highmentioning

confidence: 99%

E1- and ubiquitin-like proteins provide a direct link between protein conjugation and sulfur transfer in archaea

Miranda

Nembhard

et al. 2011

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

180

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Based on our recent work with Haloferax volcanii, ubiquitin-like (Ubl) proteins (SAMP1 and SAMP2) are known to be covalently attached to proteins in archaea. Here, we investigated the enzymes required for the formation of these Ubl-protein conjugates (SAMPylation) and whether this system is linked to sulfur transfer. Markerless in-frame deletions were generated in H. volcanii target genes. The mutants were examined for: (i) the formation of Ubl protein conjugates, (ii) growth under various conditions, including those requiring the synthesis of the sulfur-containing molybdenum cofactor (MoCo), and (iii) the thiolation of tRNA. With this approach we found that UbaA of the E1/MoeB/ThiF superfamily was required for the formation of both SAMP1-and SAMP2-protein conjugates. In addition, UbaA, SAMP1, and MoaE (a homolog of the large subunit of molybdopterin synthase) were essential for MoCo-dependent dimethyl sulfoxide reductase activity, suggesting that these proteins function in MoCo-biosynthesis. UbaA and SAMP2 were also crucial for optimal growth at high temperature and the thiolation of tRNA. Based on these results, we propose a working model for archaea in which the E1-like UbaA can activate multiple Ubl SAMPs for protein conjugation as well as for sulfur transfer. In sulfur transfer, SAMP1 and SAMP2 appear specific for MoCo biosynthesis and the thiolation of tRNA, respectively. Overall, this study provides a fundamental insight into the diverse cellular functions of the Ubl system. posttranslational modification | tRNA modification | proteasomes

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Growth Kinetics of Extremely Halophilic Archaea (Family Halobacteriaceae ) as Revealed by Arrhenius Plots

Cited by 95 publications

References 24 publications

The N-Terminal Penultimate Residue of 20S Proteasome α1 Influences its N ^α Acetylation and Protein Levels as Well as Growth Rate and Stress Responses of Haloferax volcanii

The N-Terminal Penultimate Residue of 20S Proteasome α1 Influences its N ^α Acetylation and Protein Levels as Well as Growth Rate and Stress Responses of Haloferax volcanii

Proteomic analysis of Haloferax volcanii reveals salinity-mediated regulation of the stress response protein PspA

E1- and ubiquitin-like proteins provide a direct link between protein conjugation and sulfur transfer in archaea

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Growth Kinetics of Extremely Halophilic Archaea (Family Halobacteriaceae ) as Revealed by Arrhenius Plots

Cited by 95 publications

References 24 publications

The N-Terminal Penultimate Residue of 20S Proteasome α1 Influences its N α Acetylation and Protein Levels as Well as Growth Rate and Stress Responses of Haloferax volcanii

The N-Terminal Penultimate Residue of 20S Proteasome α1 Influences its N α Acetylation and Protein Levels as Well as Growth Rate and Stress Responses of Haloferax volcanii

Proteomic analysis of Haloferax volcanii reveals salinity-mediated regulation of the stress response protein PspA

E1- and ubiquitin-like proteins provide a direct link between protein conjugation and sulfur transfer in archaea

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The N-Terminal Penultimate Residue of 20S Proteasome α1 Influences its N ^α Acetylation and Protein Levels as Well as Growth Rate and Stress Responses of Haloferax volcanii

The N-Terminal Penultimate Residue of 20S Proteasome α1 Influences its N ^α Acetylation and Protein Levels as Well as Growth Rate and Stress Responses of Haloferax volcanii