title: Maintenance of electrostatic stabilization in altered tubulin lateral contacts may facilitate formation of helical filaments in foraminifera.
abstract: Microtubules in foraminiferan protists (forams) can convert into helical filament structures, in which longitudinal intraprotofilament interactions between tubulin heterodimers are thought to be lost, while lateral contacts across protofilaments are still maintained. The coarse geometric features of helical filaments are known through low-resolution negative stain electron microscopy (EM). In this study, geometric restraints derived from these experimental data were used to generate an average atomic-scale helical filament model, which anticipated a modest reorientation in the lateral tubulin heterodimer interface. Restrained molecular dynamics (MD) simulations of the nearest neighbor interactions combined with a Genalized Born implicit solvent model were used to assess the lateral, longitudinal, and seam contacts in 13-3 microtubules and the reoriented lateral contacts in the helical filament model. This electrostatic analysis suggests that the change in the lateral interface in the helical filament does not greatly diminish the lateral electrostatic interaction. After longitudinal dissociation, the 13-3 seam interaction is much weaker than the reoriented lateral interface in the helical filament model, providing a plausible atomic-detail explanation for seam-to-lateral contact transition that enables the transition to a helical filament structure.
authors.affiliation: Laboratory of Computational and Structural Biology, Division of Genetics, Wadsworth Center, New York State Department of Health, PO Box 509, Albany, NY 12201-0509, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Bassen
authors.affiliation: Laboratory of Cellular and Molecular Basis of Diseases, Division of Translational Medicine, Wadsworth Center, New York State Department of Health, PO Box 509, Albany, NY 12201-0509, USA.
authors.forename: Yubo
authors.initials: Y
authors.lastname: Hou
authors.affiliation: Laboratory of Cellular and Molecular Basis of Diseases, Division of Translational Medicine, Wadsworth Center, New York State Department of Health, PO Box 509, Albany, NY 12201-0509, USA.|Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, USA.
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Bowser
authors.affiliation: Laboratory of Computational and Structural Biology, Division of Genetics, Wadsworth Center, New York State Department of Health, PO Box 509, Albany, NY 12201-0509, USA.|Department of Biomedical Sciences, School of Public Health, State University of New York at Albany, USA.
authors.forename: Nilesh K
authors.initials: NK
authors.lastname: Banavali
mesh_terms: D000818:Animals; D002417:Cattle; D056908:Foraminifera / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D055503:Protein Multimerization; D015800:Protozoan Proteins / Q000737:chemistry*; D055672:Static Electricity; D014404:Tubulin / Q000737:chemistry*
chemical_list: D015800:Protozoan Proteins; D014404:Tubulin