title: How calcium controls microtubule anisotropic phase formation in the presence of microtubule-associated proteins in vitro.
abstract: Here we show a new effect of Ca2+ on microtubule morphology: Ca2+ can cause smooth curving of microtubules in the presence of microtubule-associated proteins (MAPs). In vitro, microtubules self-organize, forming complex dissipative structures. Such structures may be strongly affected by relatively weak external factors. A factor such as Ca2+ potentially influences spatiotemporal patterns of microtubule assembly, but the dynamics are unclear. We tested Ca2+ effects on microtubule formation. Using EM, microtubule length, curvature, and alignment and were measured in two systems: 2 mg/ml microtubule protein containing MAPs and 1 mM EGTA with and without 1 mM Ca2+. The two systems were then tested using light scattering. In low Ca2+, a birefringent microtubular pattern is seen, increasing with polymerization. When 1 mM Ca2+ is added to the solution, anisotropic phase is prevented without microtubule disruption. This demonstrates an additional mechanism by which Ca2+ can alter the dynamics and morphology of microtubules.
authors.affiliation: Brain and Mind Research Institute, Discipline of Physiology, The University of Sydney, NSW 2006, Australia.
authors.forename: Vlado
authors.initials: V
authors.lastname: Buljan
authors.forename: Elena P
authors.initials: EP
authors.lastname: Ivanova
authors.forename: Karen M
authors.initials: KM
authors.lastname: Cullen