Dataset Information

Intermediate filament-like proteins in bacteria and a cytoskeletal function in Streptomyces.

ABSTRACT: Actin and tubulin cytoskeletons are conserved and widespread in bacteria. A strikingly intermediate filament (IF)-like cytoskeleton, composed of crescentin, is also present in Caulobacter crescentus and determines its specific cell shape. However, the broader significance of this finding remained obscure, because crescentin appeared to be unique to Caulobacter. Here we demonstrate that IF-like function is probably a more widespread phenomenon in bacteria. First, we show that 21 genomes of 26 phylogenetically diverse species encoded uncharacterized proteins with a central segmented coiled coil rod domain, which we regarded as a key structural feature of IF proteins and crescentin. Experimental studies of three in silico predicted candidates from Mycobacterium and other actinomycetes revealed a common IF-like property to spontaneously assemble into filaments in vitro. Furthermore, the IF-like protein FilP formed cytoskeletal structures in the model actinomycete Streptomyces coelicolor and was needed for normal growth and morphogenesis. Atomic force microscopy of living cells revealed that the FilP cytoskeleton contributed to mechanical fitness of the hyphae, thus closely resembling the function of metazoan IF. Together, the bioinformatic and experimental data suggest that an IF-like protein architecture is a versatile design that is generally present in bacteria and utilized to perform diverse cytoskeletal tasks.

SUBMITTER: Bagchi S

PROVIDER: S-EPMC2680258 | biostudies-literature | 2008 Nov

REPOSITORIES: biostudies-literature

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Intermediate filament-like proteins in bacteria and a cytoskeletal function in Streptomyces.

Bagchi Sonchita S Tomenius Henrik H Belova Lyubov M LM Ausmees Nora N

Molecular microbiology 20081002 4

Actin and tubulin cytoskeletons are conserved and widespread in bacteria. A strikingly intermediate filament (IF)-like cytoskeleton, composed of crescentin, is also present in Caulobacter crescentus and determines its specific cell shape. However, the broader significance of this finding remained obscure, because crescentin appeared to be unique to Caulobacter. Here we demonstrate that IF-like function is probably a more widespread phenomenon in bacteria. First, we show that 21 genomes of 26 phy ...[more]

PMID: 18976278

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Project description:Intermediate filament (IF) proteins assemble into highly flexible filaments that organize into complex cytoplasmic networks: keratins in all types of epithelia, vimentin in endothelia, and desmin in muscle. Since IF elongation proceeds via end-to-end annealing of unit-length filaments and successively of progressively growing filaments, it is important to know how their remarkable flexibility, i.e., their persistence length lp, influences the assembly kinetics. In fact, their lp ranges between 0.3 μm (keratin K8/K18) and 1.0 μm (vimentin and desmin), and thus is orders of magnitude lower than that of microtubules and F-actin. Here, we present a unique mathematical model, which implements the semiflexible nature of the three IF types based on published semiflexible polymers theories and depends on a single free parameter k0. Calibrating this model to filament mean length dynamics of the three proteins, we demonstrate that the persistence length is indeed essential to accurately describe their assembly kinetics. Furthermore, we reveal that the difference in flexibility alone does not explain the significantly faster assembly rate of keratin filaments compared with that of vimentin. Likewise, desmin assembles approximately six times faster than vimentin, even though both their filaments exhibit the same lp value. These data strongly indicate that differences in their individual amino acid sequences significantly impact the assembly rates. Nevertheless, using a single k0 value for each of these three key representatives of the IF protein family, our advanced model does accurately describe the length distribution and mean length dynamics and provides effective filament assembly rates. It thus provides a tool for future investigations on the impact of posttranslational modifications or amino acid changes of IF proteins on assembly kinetics. This is an important issue, as the discovery of mutations in IF genes causing severe human disease, particularly for desmin and keratins, is steadily increasing.

Dataset Information

Intermediate filament-like proteins in bacteria and a cytoskeletal function in Streptomyces.

Publications

Intermediate filament-like proteins in bacteria and a cytoskeletal function in Streptomyces.

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