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Molecular mechanisms of the interhead coordination by interhead tension in cytoplasmic dyneins.

ABSTRACT: Cytoplasmic dyneins play a major role in retrograde cellular transport by moving vesicles and organelles along microtubule filaments. Dyneins are multidomain motor proteins with two heads that coordinate their motion via their interhead tension. Compared with the leading head, the trailing head has a higher detachment rate from microtubules, facilitating the movement. However, the molecular mechanism of such coordination is unknown. To elucidate this mechanism, we performed molecular dynamics simulations on a cytoplasmic dynein with a structure-based coarse-grained model that probes the effect of the interhead tension on the structure. The tension creates a torque that influences the head rotating about its stalk. The conformation of the stalk switches from the ? registry to the ? registry during the rotation, weakening the binding affinity to microtubules. The directions of the tension and the torque of the leading head are opposite to those of the trailing head, breaking the structural symmetry between the heads. The leading head transitions less often to the ? registry than the trailing head. The former thus has a greater binding affinity to the microtubule than the latter. We measured the moment arm of the torque from a dynein structure in the simulations to develop a phenomenological model that captures the influence of the head rotating about its stalk on the differential detachment rates of the two heads. Our study provides a consistent molecular picture for interhead coordination via interhead tension.

SUBMITTER: Wang Q

PROVIDER: S-EPMC6176594 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Molecular mechanisms of the interhead coordination by interhead tension in cytoplasmic dyneins.

Wang Qian Q Jana Biman B Diehl Michael R MR Cheung Margaret S MS Kolomeisky Anatoly B AB Onuchic José N JN

Proceedings of the National Academy of Sciences of the United States of America 20180917 40

Cytoplasmic dyneins play a major role in retrograde cellular transport by moving vesicles and organelles along microtubule filaments. Dyneins are multidomain motor proteins with two heads that coordinate their motion via their interhead tension. Compared with the leading head, the trailing head has a higher detachment rate from microtubules, facilitating the movement. However, the molecular mechanism of such coordination is unknown. To elucidate this mechanism, we performed molecular dynamics si ...[more]

PMID: 30224489

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Project description:Oxidative stress (OS) results from genetic defects or stressful environmental challenges that cause unchecked production of reactive oxygen species (ROS). OS has been implicated in many diseases due to its wide ranging damage to nucleic acids, proteins and lipids. Using Halobacterium salinarum NRC-1, an extremophile that thrives under conditions of excessive OS, we have constructed a systems model for oxidative stress response (OSR) by integrating transcriptional changes induced by treatments with H2O2 and paraquat, functional associations inferred through comparative genomics, and de novo discovered cis-regulatory motifs. Together with phenotypic analysis of mutant strains this has revealed a multi-tiered OS management program to transcriptionally coordinate three peroxidase/catalase enzymes, two superoxide dismutases, production of rhodopsins, carotenoids, and gas vesicles, metal trafficking, and various other aspects of metabolism. Remarkably, a significant fraction of this OSR was accurately recapitulated by a model that was previously constructed from cellular responses to diverse environmental perturbations –this constitutes the general stress response component. Notwithstanding this observation, comparison of the two models has identified the coordination of frontline defense and repair systems by regulatory mechanisms that are triggered uniquely by severe OS and not by other environmental stressors, including sub-inhibitory levels of redox-active metals, extreme changes in oxygen tension, and a sub-lethal dose of g rays. Mid-log phase cultures of H. salinarum NRC-1 (2 biological replicates) grown in flasks were treated with either sub-lethal concentrations of 25mM H2O2 or 4mM PQ and incubated with shaking for up to 240 min. For each treatment, two time courses were run to determine the transcriptional responses to (1) constant stress and (2) recovery of H. salinarum NRC-1 to H2O2 and PQ. During constant stress, culture aliquots (~4ml) were collected over a time course (-1, 5, 10, 20, 40, 80 and 160 minutes), centrifuged (16000g, 90 seconds) and flash frozen. For recovery, cells were first treated for 2-hours with either 25 mM H2O2 or 4mM PQ, recovered by centrifugation, washed and re-suspended in CM. Cultures were returned to the incubator with shaking and samples were taken at 0, 10, 20, 30, 40, 50, 60, 120, and 240 minutes and processed as described previously. Analysis of temporal transcriptional changes (-1, 0, 5, 10, 20, 40, 80, 160 and 320m) to sub-inhibitory concentrations of PQ (0.25mM) was also characterized. Total RNA was prepared and labeled with Alexa547 and Alexa647 dyes. Intensities were normalized between the Alexa 546 and Alexa 647 channels by scaling all intensities in one channel such that the 75th percentile in each channel was made equal.

Dataset Information

Molecular mechanisms of the interhead coordination by interhead tension in cytoplasmic dyneins.

Publications

Molecular mechanisms of the interhead coordination by interhead tension in cytoplasmic dyneins.

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