title: Actin bundling and polymerisation properties of eukaryotic elongation factor 1 alpha (eEF1A), histone H2A-H2B and lysozyme in vitro.
abstract: Elongation factor 1 alpha (eEF1A) is a positively charged protein which has been shown to interact with the actin cytoskeleton. However, to date, a specific actin binding site within the eEF1A sequence has not been identified and the mechanism by which eEF1A interacts with actin remains unresolved. Many protein-protein interactions occur as a consequence of their physicochemical properties and actin bundle formation has been shown to result from non-specific electrostatic interaction with basic proteins. This study investigated interactions between actin, eEF1A and two other positively charged proteins which are not regarded as classic actin binding proteins (namely lysozyme and H2A-H2B) in order to compare their actin organising effects in vitro. For the first time using atomic force microscopy (AFM) we have been able to image the interaction of eEF1A with actin and the subsequent bundling of actin in vitro. Interestingly, we found that eEF1A dramatically increases the rate of polymerisation (45-fold above control levels). We also show for the first time that H2A-H2B has remarkably similar effects upon actin bundling (relative bundle size/number) and polymerisation (35-fold increase above control levels) as eEF1a. The presence of lysozyme resulted in bundles which were distinct from those formed due to eEF1A and H2A-H2B. Lysozyme also increased the rate of actin polymerisation above the control level (by 10-fold). Given the striking similarities between the actin bundling and polymerisation properties of eEF1A and H2A-H2B, our results hint that dimerisation and electrostatic binding may provide clues to the mechanism through which eEF1A-actin bundling occurs.
authors.affiliation: School of Pharmacy & Biomolecular Sciences, Liverpool John Moore University, Liverpool, UK. a.doyle@2003.ljmu.ac.uk
authors.forename: Annette
authors.initials: A
authors.lastname: Doyle
authors.forename: Steven R
authors.initials: SR
authors.lastname: Crosby
authors.forename: David R
authors.initials: DR
authors.lastname: Burton
authors.forename: Francis
authors.initials: F
authors.lastname: Lilley
authors.forename: Mark F
authors.initials: MF
authors.lastname: Murphy
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000648:ultrastructure; D000199:Actins / Q000737:chemistry* / Q000648:ultrastructure; D000818:Animals; D002645:Chickens; D006657:Histones / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D009113:Muramidase / Q000737:chemistry*; D020648:Peptide Elongation Factor 1 / Q000737:chemistry*; D058105:Polymerization; D011485:Protein Binding; D011487:Protein Conformation; D011721:Pyrenes / Q000737:chemistry; D011817:Rabbits; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*; D055672:Static Electricity
chemical_list: D000199:Actins; D006657:Histones; D020648:Peptide Elongation Factor 1; D011721:Pyrenes; D029701:Saccharomyces cerevisiae Proteins; C030984:pyrene; D009113:Muramidase