Stortelder Aike, Hendriks Johnny, Buijs Joost B, Bulthuis Jaap, Gooijer Cees, van der Vies Saskia M, van der Zwan Gert
Laser Centre VU, Department of Analytical Chemistry and Applied Spectroscopy, Vrije Universiteit, Faculty of Sciences, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
J Phys Chem B. 2006 Dec 14;110(49):25050-8. doi: 10.1021/jp064881t.
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.
利用内在蛋白荧光团色氨酸的时间分辨荧光和稳态荧光对噬菌体T4衣壳蛋白gp23进行了研究。体外gp23在低温下主要由单体组成，但在室温下形成六聚体。为了拓展我们对gp23结构和六聚化特性的认识，将色氨酸突变体（W13V）的温度依赖性荧光特性与野生型gp23的进行了比较。W13V突变位于该蛋白的N端部分，在活噬菌体中前头部形成后该部分会被切除。结果表明，W13在六聚化过程中发挥作用，但六聚体形成后稳定六聚体并不需要它。此外，除了单体到六聚体的温度转变（野生型和W13V gp23分别为15 - 23℃和12 - 43℃），我们还能观察到六聚体野生型gp23的N端在40℃左右发生变性。另外，借助最近发表的gp23同源模型，从时间分辨荧光测量获得的寿命可以初步归属于特定的色氨酸残基。
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