The Bacterial Flagella and the Flagellar Protein Flagellin

Abstract

In comparison with the relatively complicated flagella of all nucleated organisms, most of the actively motile bacteria have very much simpler locomotion organelles. These flagella are long thin filaments with a helical superstructure, anchored at one end in the cell membrane. Helical waves pass along the flagella in the distal direction during locomotion. In the flagella, identical structural units of a single protein species, flagellin, are linked to one another by non-covalent bonds. The flagellin subunits can be separated from one another by mild methods, and their biochemistry as well as their structure and morphology can be investigated in the isolated state. Under certain conditions they can reaggregate in r h o to form polymorphous helical filaments, which are practically indistinguishable from intact flagella. In the flagellum, the elongated flagellin molecules have a layered arrangement in about ten parallel strands, which in turn form a hollow cylinder. Since this cylinder is deformed into a large helix, the individual chemically identical flagellin protomers and the protomer strands in the helical flagella are only quasi-equivalent. The conformation and bonding pattern of the individual longitudinal flagellin lines can presumably be controlled in cico by the basal structures. so that movement within the flagellum could conceivably occur as follows. A cyclically induced change in the length of the individual strands could result in an apparent rotation of the helical flagellum. According to hydrodynamic calculations, the resulting forward thrust is sufficient to propel the bacteria at the observed speeds of up to 50 pm,k.

Characterization of Flagellar Filaments and Flagellin through Optical Microscopy and Label-Free Nanopore Responsiveness

“…Optical imaging, as expected, did not provide any substantial information about flagellin, where they appeared as indiscernible fluorescent dots (Figure S1). The radii of flagellin were also calculated using nanopore-based excluded electrolyte volume at each of the depolymerization temperatures and were found to be ∼4.2 ± 0.2 nm, ∼4.3 ± 0.3 nm, ∼4.1 ± 0.2 nm, and ∼4.7 ± 0.5 nm for ∼65 °C, ∼70 °C, ∼75 °C, and ∼80 °C, respectively, which are in good agreement with the literature reported values (4–5 nm). ,, The close agreement of the molecular radii suggests that aggregation of these flagellin proteins above the commonly used T depol (∼65 °C) may not take place in the temperature range used in this study. We have attributed the changes in the Δ G (Figure ) and translocation time (Figures S11 and S12) profiles as a result of depolymerization at ∼75 °C and ∼80 °C to changes in the protein charge (both Δ G and translocation time depend on the analyte charge), , which may have arisen due to protein misfolding caused by irreversible changes to the protein native structure at these higher temperatures.…”

The flagellar filament protein

“…Although the amino acid sequences are known for a few flagellins (see below), no one has yet been able to "grow" a crystal suitable for X-ray analysis and only theoretical models are available for the three-dimensional structure of flagellins (Bode 1973;Calladine 1976).…”

Toll‐like receptors in health and disease

“…258 This difference might be related to high levels of bacterial attachment in the oral cavity, [259][260][261] where flagellin is a component of the bacterial flagellum anchored at one end of the cell membrane. 262 According to a study by Chen et al, 263 more than 60% of BCs express the TL5 protein. TLR5 overexpression had a positive correlation with lymph node metastasis and a negative correlation with histological grade.…”

“…They further found that TLR5 expression levels were also greater in oral cancers than in skin cancers and concluded that TLR5 is usually activated more endogenously in oral cancers 258 . This difference might be related to high levels of bacterial attachment in the oral cavity, 259–261 where flagellin is a component of the bacterial flagellum anchored at one end of the cell membrane 262 …”

“… 258 This difference might be related to high levels of bacterial attachment in the oral cavity, 259 , 260 , 261 where flagellin is a component of the bacterial flagellum anchored at one end of the cell membrane. 262 …”