Venables, Neil A. (2015) The electrostatic analysis of TOG-domains from XMAP215/DIS1 family members. PhD thesis, University of Warwick.

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Abstract

TOG domain MT polymerases are catalysts of MT dynamics that track MT tips and chaperone tubulin exchange by mechanisms that are not yet understood. In this work, we use computational simulation to probe the detailed mechanisms by which TOGs capture and manipulate GTP-tubulin.

Natural TOGs display a ridge of basic surface loops that forms the core of the TOG-tubulin interface. Computational mutagenesis shows that these basic loops play a dominant role in setting the overall electrostatic field on the TOG domain, and that natural TOGs fall into subclasses depending on the detailed structure of these fields. Normal mode analysis reveals that natural TOG domains show characteristic patterns of flexibility that define their position within the TOG array. Nonetheless all TOGs are sufficiently stiff that the range of positions explored by the domains’ common secondary structure is heavily restricted. Brownian dynamics simulations establish that diffusion-to-capture of tubulin by TOG domains is very strongly electrostatically steered. In all trajectories examined, TOGs were initially captured and oriented by tubulin to a degree that reflects their simulated association rates.

To be effective, TOG domain MT polymerases need to capture GTP-tubulin rapidly and specifically from solution and configure it so that it incorporates readily at the growing MT tip. Our data show that TOGs do this (1) by optimising long range, electrostatically-steered diffusion-to-capture, which is important for creating a tethered complex at the MT tip, and (2) by using conformational selection within the tethered complex to drive GTP-tubulin into conformation(s) that favours assembly and dissociation of the complex upon lattice incorporation.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QR Microbiology
Library of Congress Subject Headings (LCSH):	Overexpression (Genetics)
Official Date:	September 2015
Dates:	Date Event September 2015 Submitted
Institution:	University of Warwick
Theses Department:	Systems Biology Doctoral Training Centre
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Cross, R. A. ; Bretschneider, Till
Extent:	xiv, 131 leaves : illustrations (colour), charts.
Language:	eng

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