Crenactin forms actin-like double helical filaments regulated by arcadin-2

Izoré, Thierry; Kureisaite-Ciziene, Danguole; McLaughlin, Stephen H.; Löwe, Jan

doi:10.7554/elife.21600

Cited by 41 publications

(28 citation statements)

References 51 publications

(113 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The two strands are parallel and offset by a half-subunit stagger. The repeat distance is considerably shorter than found in other actins, which range from 512 to 834 Å (27)(28)(29)(30)(31)(32), yielding a highly twisted AlfA filament with only 8 subunits per turn of the two-start helix. The filament has a left-handed two-start twist, confirming our previous determination of handedness by tomographic reconstruction of negatively stained AlfA filaments (9).…”

Section: Resultsmentioning

confidence: 72%

Cryo-EM structure of the bacterial actin AlfA reveals unique assembly and ATP-binding interactions and the absence of a conserved subdomain

Usluer

DiMaio

Yang

et al. 2017

Preprint

View full text Add to dashboard Cite

Bacterial actins are an evolutionarily diverse family of ATP-dependent filaments built from protomers with a conserved structural fold. Actin-based segregation systems are encoded on many bacterial plasmids and function to partition plasmids into daughter cells. The bacterial actin AlfA segregates plasmids by a mechanism distinct from other partition systems, dependent on its unique dynamic properties. Here, we report the near-atomic resolution cryo-EM structure of the AlfA filament, which reveals a strikingly divergent filament architecture resulting from the loss of a subdomain conserved in all other actins and a novel mode of ATP binding. Its unusual assembly interfaces and nucleotide interactions provide insight into AlfA dynamics, and expand the range of evolutionary variation accessible to actin quaternary structure. Significance StatementActin filaments are dynamic cytoskeletal elements that assemble upon ATP binding. Actin homologs are present in all domains of life, and all share a similar three-dimensional structure of the assembling subunit, but evolutionary changes to subunit have generated many different actin filament structures. The filament structure of the bacterial actin AlfA, which positions plasmids -small, circular DNA molecules that encode important genes -to ensure that each daughter cell receives a copy at cell division. AlfA is different from all other actins in two critical ways: it binds to ATP in a unique way, and it is missing a quarter of the conserved structural core. These differences explain unusual AlfA assembly dynamics that underlie its ability to move plasmids.

show abstract

Section: Resultsmentioning

confidence: 72%

Cryo-EM structure of the bacterial actin AlfA reveals unique assembly and ATP-binding interactions and the absence of a conserved subdomain

Usluer

DiMaio

Yang

et al. 2017

Preprint

View full text Add to dashboard Cite

show abstract

“…The analysis was carried out with conventional, room temperature EM using negatively stained samples, which limited the resolution to around 15 Å. To obtain a detailed, near-atomic model of the filament structure, we turned to cryo-EM, which has recently shown much success in providing such information for actin, ParM, MamK and crenactin filaments (4,5,10,19).…”

Section: Resultsmentioning

confidence: 99%

“…The AlfA monomer structure shows a subdomain deletion and an unusual nucleotide-binding mode. For all previous actin-like filament structures determined by cryo-EM, reliable structures of the monomer obtained by X-ray crystallography were available to guide model building (4,5,10). With AlfA, such aid was not at hand, and our efforts to crystallise AlfA yielded only poorly diffracting crystals.…”

Section: Resultsmentioning

confidence: 99%

“…Within the archaeal phylum Crenarcheota, actin-like protein crenactin has been identified, and has been shown to be the closest so far in filament architecture and monomer fold to eukaryotic actin. The function of crenactin remains to be elucidated (5). In addition to the housekeeping roles described above, a separate functional group evolved in the actin-like family to aid the replication of certain low copy-number plasmids, where actin-like filaments enable efficient segregation of plasmid DNA.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cryo-EM reconstruction of AlfA fromBacillus subtilisreveals the structure of a simplified actin-like filament at 3.4 Å resolution

Harris

Löwe

2017

Preprint

Self Cite

View full text Add to dashboard Cite

Low copy-number plasmid pLS32 of Bacillus subtilis subsp. natto contains a partitioning system that ensures segregation of plasmid copies during cell division. The partitioning locus comprises actin-like protein AlfA, adaptor protein AlfB and the centromeric sequence parN. Similar to the ParMRC partitioning system from E. coli plasmid R1, AlfA filaments form actin-like double helical filaments that arrange into an antiparallel bipolar spindle, which attaches its growing ends to sister plasmids, through interactions with AlfB and parN. Since, compared with ParM and other actin-like proteins, AlfA is highly diverged in sequence, we determined the atomic structure of non-bundling AlfA filaments to 3.4 Å resolution by cryo-EM. The structure reveals how the deletion of subdomain IIB of the canonical actin-fold has been accommodated by unique longitudinal and lateral contacts, whilst still enabling formation of left-handed, double helical, polar and staggered filaments that are architecturally similar to ParM. Through cryo-EM reconstruction of bundling AlfA filaments we obtained a pseudo-atomic model of AlfA doublets: the assembly of two filaments. The filaments are antiparallel, as required by the segregation mechanism, and exactly anti-phasic with 8-fold integer helical symmetry, to enable efficient doublet formation. The structure of AlfA filaments and doublets shows, in atomic detail, signs of the strong evolutionary pressure for simplicity, placed on plasmids: deletion of an entire domain of the actin fold is compensated by changes to all interfaces so that the required properties of polymerisation, nucleotide hydrolysis and antiparallel doublet formation are retained to fulfil the system's biological raison d'être. Significance StatementProtein filaments perform a vast array of functions inside almost all living cells. Actin-like proteins in archaea and bacteria have previously been found to form a surprising diversity of filament architectures, reflecting their divergent cellular roles. Actin-like AlfA is unique in that it is much smaller than all other filament forming actin-like proteins. With an atomic structure of the AlfA filament, obtained by high-resolution electron cryo-microscopy, we have revealed-at atomic level of detail-how AlfA filaments form dynamic filaments capable of transporting plasmid DNA in cells and how these filaments arrange into antiparallel bundles required for the segregation mechanism.

show abstract

“…Now, in eLife, Löwe and colleagues – including Izoré as first author – have used electron cryo-microscopy to further investigate the structure of crenactin filaments (Izoré et al, 2016). However, contrary to the previous reports, Izoré et al now show that crenactin filaments are more similar to actin filaments than previously thought.…”

mentioning

confidence: 99%