title: Hexamerization of the bacteriophage T4 capsid protein gp23 and its W13V mutant studied by time-resolved tryptophan fluorescence.
abstract: The bacteriophage T4 capsid protein gp23 was studied using time-resolved and steady-state fluorescence of the intrinsic protein fluorophore tryptophan. In-vitro gp23 consists mostly of monomers at low temperature but forms hexamers at room temperature. To extend our knowledge of the structure and hexamerization characteristics of gp23, the temperature-dependent fluorescence properties of a tryptophan mutant (W13V) were compared to those of wild-type gp23. The W13V mutation is located in the N-terminal part of the protein, which is cleaved off after prohead formation in the live bacteriophage. Results show that W13 plays a role in the hexamerization process but is not needed to stabilize the hexamer once it is formed. Furthermore, besides the monomer-to-hexamer temperature transition (15-23 degrees C and 12-43 degrees C for wild-type and W13V gp23, respectively), we were able to observe denaturation of the N-terminus in hexameric wild-type gp23 around 40 degrees C. In addition, with the aid of a recently published homology model of gp23, the lifetimes obtained from time-resolved fluorescence measurements could tentatively be assigned to specific tryptophan residues.
authors.affiliation: Laser Centre VU, Department of Analytical Chemistry and Applied Spectroscopy, Vrije Universiteit, Faculty of Sciences, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
authors.forename: Aike
authors.initials: A
authors.lastname: Stortelder
authors.forename: Johnny
authors.initials: J
authors.lastname: Hendriks
authors.forename: Joost B
authors.initials: JB
authors.lastname: Buijs
authors.forename: Jaap
authors.initials: J
authors.lastname: Bulthuis
authors.forename: Cees
authors.initials: C
authors.lastname: Gooijer
authors.forename: Saskia M
authors.initials: SM
authors.lastname: van der Vies
authors.forename: Gert
authors.initials: G
authors.lastname: van der Zwan
mesh_terms: D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D013050:Spectrometry, Fluorescence; D013997:Time Factors; D014364:Tryptophan / Q000737:chemistry*; D014633:Valine / Q000737:chemistry*
chemical_list: D036022:Capsid Proteins; C064517:gp23 protein, Bacteriophage T4; D014364:Tryptophan; D014633:Valine