The isolation of cod muscle tropomyosin by heat treatment

Anti-adhesive properties of fish tropomyosins

AIMS

We have recently found that preconditioning of stainless steel surfaces with an aqueous fish muscle extract can significantly impede bacterial adhesion. The purpose of this study was to identify and characterize the primary components associated with this bacteria-repelling effect.

METHODS AND RESULTS

The anti-adhesive activity was assayed against Escherchia coli K-12, and bacterial adhesion was quantified by crystal violet staining and sonication methods. Proteolytic digestion, elution and fractionation experiments revealed that the anti-adhesive activity of the extract was linked to the formation of a proteinaceous conditioning film composed primarily of fish tropomyosins. These fibrous proteins formed a considerable anti-adhesive conditioning layer on and reduced bacterial adhesion to several different materials including polystyrene, vinyl plastic, stainless steel and glass. The protein adsorption profiles obtained from the various materials did not differ significantly, but elution was often incomplete making minor qualitative/quantitative differences indiscernible.

CONCLUSIONS

The data highlights the significance of protein conditioning films on bacterial adhesion and emphasizes the importance of substratum's physiochemical properties and exposure time with regards to protein adsorption/elution efficiency and subsequent bacterial adhesion.

SIGNIFICANCE AND IMPACT OF THE STUDY

Fish tropomyosin-coatings could potentially offer a nontoxic and relatively inexpensive measure of reducing bacterial colonization of inert surfaces.

Fish fast skeletal muscle tropomyosins show species-specific thermal stability

Tropomyosin (TM) was isolated from the fast skeletal muscle of six fish species, whose amino acid sequences of this protein have already been revealed. The thermal stability of these TMs was measured by differential scanning calorimetry (DSC) and circular dichroism (CD), while the molecular weights were measured by mass spectrometry. The results showed clear differences in thermostability among these fish TMs, though the identity of amino acid sequences was more than 93.3%. Therefore, only a few amino acid substitutions could affect the overall stability of the TM molecule. Especially, several residues located on the molecular surface were considered to be responsible for such stability difference. In contrast, the molecular weights of these TMs as measured by mass spectrometry were higher than those calculated from amino acid composition, suggesting the presence of post-translational modification(s) which could also affect their thermal stability.

Isolation and characterization of tropomyosin from fish muscle

A comprehensive survey of tropomyosin from various fish myotomal muscles is reported. The fish tropomyosins were blocked at the N-terminus and, as expected, were found to be of similar amino acid composition, alpha-helical content (> 90% at 10 degrees C) and molecular weight to other vertebrate striated muscle forms. The tropomyosins of salmonids and herring muscle were noticeably heterogeneous when assessed by 2D-PAGE. The distribution of isoforms was tissue-specific: slow muscle contained alpha-type tropomyosin while fast muscle contained beta-type tropomyosin. In other species (cod, haddock, wolf-fish and sharks) alpha-type tropomyosins were present in both kinds of muscle but beta-tropomyosin was absent.