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- Gan, Lu, et al.
(author)
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Capsid Conformational Sampling in HK97 Maturation Visualized by X-Ray Crystallography and Cryo-EM
- 2006
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In: Structure. - : Elsevier BV. - 0969-2126 .- 1878-4186. ; 14:11, s. 1655-1665
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Journal article (peer-reviewed)abstract
- Maturation of the bacteriophage HK97 capsid from a precursor (Prohead II) to the mature state (Head II) involves a 60 angstrom radial expansion. The mature particle is formed by 420 copies of the major capsid protein organized on a T = 7 laevo, lattice with each subunit covalently crosslinked to two neighbors. Well-characterized pH 4 expansion intermediates make HK97 valuable for investigating quaternary structural dynamics. Here, we use X-ray crystallography and cryo-EM to demonstrate that in the final transition in maturation (requiring neutral pH), pentons in Expansion Intermediate IV (EI-IV) reversibly sample 14 angstrom translations and 6 degrees rotations relative to a fixed hexon lattice. The limit of this trajectory corresponds to the Head II conformation that is secured at this extent only by the formation of the final class of covalent crosslinks. Mutants that cannot crosslink or EI-IV particles that have been rendered incapable of forming the final crosslink remain in the EI-IV state.
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- Golmohammadi, R, et al.
(author)
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The crystal structure of bacteriophage Q beta at 3.5 angstrom resolution
- 1996
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In: STRUCTURE. - : CURRENT BIOLOGY LTD. - 0969-2126. ; 4:5, s. 543-554
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Journal article (other academic/artistic)abstract
- Background: The capsid protein subunits of small RNA bacteriophages form a T=3 particle upon assembly and RNA encapsidation. Dimers of the capsid protein repress translation of the replicase gene product by binding to the ribosome binding site and this in
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- Hammarlöf, Disa L., et al.
(author)
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Temperature-sensitive mutants of RNase E in Salmonella enterica
- 2011
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In: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 193:23, s. 6639-6650
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Journal article (peer-reviewed)abstract
- RNase E has an important role in mRNA turnover and stable RNA processing although the reason for its essentiality is unknown. We isolated conditional mutants of RNase E to provide genetic tools to probe its essential function. In Salmonella enterica serovar Typhimurium an extreme slow-growth phenotype caused by mutant EF-Tu (Gln125Arg, tufA499) can be rescued by mutants of RNase E that have reduced activity. We exploited this phenotype to select mutations in RNase E and screened these for temperature sensitivity (ts) for growth. Four different ts mutations were identified, all in the N-terminal domain of RNase E: Gly66→Cys; Ile207→Ser; Ile207→Asn; Ala327→Pro. We also selected second-site mutations in RNase E that reversed temperature-sensitivity. The complete set of RNase E mutations (53 primary mutations including the ts mutations, and 23 double mutations) were analyzed for their possible effects on the structure and function of RNase E using the available 3-D structures. Most single mutations were predicted to destabilize the structure while second-site mutations that reversed the ts phenotype were predicted to restore stability to the structure. Three isogenic strain pairs carrying single or double mutations in RNase E (ts, and ts plus second-site mutation) were tested for their effects on the degradation, accumulation and processing of mRNA, rRNA and tRNA. The greatest defect was observed on rne mRNA autoregulation and this correlated with ability to rescue the tufA499-associated slow growth phenotype. This is consistent with the RNase E mutants being defective in initial binding or subsequent cleavage of an mRNA critical for fast growth.
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- Liljas, L
(author)
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Viruses
- 1996
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In: CURRENT OPINION IN STRUCTURAL BIOLOGY. - : CURRENT BIOLOGY LTD. - 0959-440X. ; 6:2, s. 151-156
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Journal article (other academic/artistic)abstract
- The structures of the components of large and complex viruses, determined over the past year, have demonstrated the great variation in the ways in which viruses achieve their goals. The structure of the bluetongue virus coat protein provides clues as to h
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