Abstract:
:Transmembrane bacterial chemoreceptors are extended, rod-shaped homodimers with ligand-binding sites at one end and interaction sites for signaling complex formation and histidine kinase control at the other. There are atomic-resolution structures of chemoreceptor fragments but not of intact, membrane-inserted receptors. Electron tomography of in vivo signaling complex arrays lack distinct densities for chemoreceptor rods away from the well-ordered base plate region, implying structural heterogeneity. We used negative staining, transmission electron microscopy, and image analysis to characterize the molecular shapes of intact homodimers of the Escherichia coli aspartate receptor Tar rendered functional by insertion into nanodisc-provided E. coli lipid bilayers. Single-particle analysis plus tomography of particles in a three-dimensional matrix revealed two bend loci in the chemoreceptor cytoplasmic domain, (i) a short, two-strand gap between the membrane-proximal, four-helix-bundle HAMP (histidine kinases, adenylyl cyclases, methyl-accepting chemoreceptors, and phosphatases) domain and the membrane-distal, four-helix coiled coil and (ii) aligned glycines in the extended, four-helix coiled coil, the position of a bend noted in the previous X-ray structure of a receptor fragment. Our images showed HAMP bends from 0° to ∼13° and glycine bends from 0° to ∼20°, suggesting that the loci are flexible hinges. Variable hinge bending explains indistinct densities for receptor rods outside the base plate region in subvolume averages of chemotaxis arrays. Bending at flexible hinges was not correlated with the chemoreceptor signaling state. However, our analyses showed that chemoreceptor bending avoided what would otherwise be steric clashes between neighboring receptors that would block the formation of core signaling complexes and chemoreceptor arrays.IMPORTANCE This work provides new information about the shape of transmembrane bacterial chemoreceptors, crucial components in the molecular machinery of bacterial chemotaxis. We found that intact, lipid-bilayer-inserted, and thus functional homodimers of the Escherichia coli chemoreceptor Tar exhibited bends at two flexible hinges along their ∼200-Å, rod-like, cytoplasmic domains. One hinge was at the short, two-strand gap between the membrane-proximal, four-helix-bundle HAMP (histidine kinases, adenylyl cyclases, methyl-accepting chemoreceptors, and phosphatases) domain and the membrane-distal, four-helix coiled coil. The other hinge was at aligned glycines in the extended, four-helix coiled coil, where a bend had been identified in the X-ray structure of a chemoreceptor fragment. Our analyses showed that flexible hinge bending avoided structural clashes in chemotaxis core complexes and their arrays.
journal_name
J Bacterioljournal_title
Journal of bacteriologyauthors
Akkaladevi N,Bunyak F,Stalla D,White TA,Hazelbauer GLdoi
10.1128/JB.00593-17subject
Has Abstractpub_date
2018-02-07 00:00:00issue
5eissn
0021-9193issn
1098-5530pii
JB.00593-17journal_volume
200pub_type
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journal_title:Journal of bacteriology
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abstract::The first alkaline phosphatase (APase) structural gene mutant of Bacillus subtilis 168 was constructed by using a clone identified by hybridization to a synthetic degenerative oligonucleotide. The design of the probe was based on the first 29 amino acids of the sequenced mature APase III protein, which had been isolat...
journal_title:Journal of bacteriology
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journal_title:Journal of bacteriology
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journal_title:Journal of bacteriology
pub_type: 杂志文章
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journal_title:Journal of bacteriology
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更新日期:1963-01-01 00:00:00
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journal_title:Journal of bacteriology
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pub_type: 杂志文章
doi:10.1128/JB.121.3.975-982.1975
更新日期:1975-03-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.168.2.688-693.1986
更新日期:1986-11-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.148.2.697-711.1981
更新日期:1981-11-01 00:00:00
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journal_title:Journal of bacteriology
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更新日期:1992-10-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.172.3.1667-1669.1990
更新日期:1990-03-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.170.3.1245-1253.1988
更新日期:1988-03-01 00:00:00
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pub_type: 杂志文章
doi:10.1128/JB.107.1.1-7.1971
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.154.3.1315-1322.1983
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journal_title:Journal of bacteriology
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更新日期:1964-11-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.171.3.1340-1345.1989
更新日期:1989-03-01 00:00:00
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更新日期:2010-10-01 00:00:00
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pub_type: 杂志文章
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更新日期:2005-08-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.121.3.1189-1199.1975
更新日期:1975-03-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
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journal_title:Journal of bacteriology
pub_type: 杂志文章
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.180.21.5619-5625.1998
更新日期:1998-11-01 00:00:00
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journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/jb.171.2.643-649.1989
更新日期:1989-02-01 00:00:00
abstract::Methanogenesis from the non-physiological C1 donors thioproline, thiazolidine, hexamethylenetetramine, formaldehyde (HCHO), and HOCH2-S-coenzyme M (CoM) was catalyzed by cell extracts of Methanobacterium thermoautotrophicum under a hydrogen atmosphere. Tetrahydromethanopterin (H4MPT) and HS-CoM were required in the re...
journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.161.2.696-701.1985
更新日期:1985-02-01 00:00:00
abstract::Many streptococcal pathogens require a polysaccharide capsule for survival in the host during systemic infection. The highly conserved CpsA protein is proposed to be a transcriptional regulator of capsule production in streptococci, although the regulatory mechanism is unknown. Hydropathy plots of CpsA predict an inte...
journal_title:Journal of bacteriology
pub_type: 杂志文章
doi:10.1128/JB.01098-10
更新日期:2011-01-01 00:00:00