Is the curvature of the flagellum involved in the apparent cooperativity of the dynein arms along the "9+2" axoneme?
Résumé
In a recent study (Cibert, C. (2008), Journal of Theoretical Biology, 253: 74-89), by assuming that the walls of the microtubules are involved in cyclic compression/dilation equilibriums as a consequence of the cyclic curvature of the axoneme, it was proposed that the local adjustments of the spatial frequencies of both the dynein arms, and the β-tubulin monomers facing series, create the propagation of joint probability waves of interaction (JPI) between these two necessary partners. Modeling the occurrence of these probable interactions along the entire length of an axoneme between each outer doublet pairs (without programming any cooperative dialog between the molecular complexes) and the cyclic attachment of two facing partners, we show that the active couples such constituted are clustered. Along a cluster the dynein arms exhibit a small phase shift with respect to the order according to which they began each their cycle after being linked to a β-tubulin monomer. The numbers of couples included in these clusters depend on the probability of interaction between the dynein arms and the β-tubulin, on the location of the outer doublet pairs around the axonemal cylinder, and on the local bending of the axoneme; around the axonemal cylinder, the faster and larger the sliding, the shorter the clusters. This mechanism could be involved in the apparent cooperativity of the molecular motors and the β-tubulin monomers, since it is partially controlled by the local curvature, and the cluster length is inversely proportional to the sliding activity of the outer doublet pairs they link.
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