Hexamerization of the bacteriophage T4 capsid protein gp23 and its W13V mutant studied by time-resolved tryptophan fluorescence.
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.
Stortelder
Aike
A
Laser Centre VU, Department of Analytical Chemistry and Applied Spectroscopy, Vrije Universiteit, Faculty of Sciences, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Hendriks
Johnny
J
Buijs
Joost B
JB
Bulthuis
Jaap
J
Gooijer
Cees
C
van der Vies
Saskia M
SM
van der Zwan
Gert
G
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*
D036022:Capsid Proteins; C064517:gp23 protein, Bacteriophage T4; D014364:Tryptophan; D014633:Valine