UV Raman evidence of a tyrosine in apo‐human serum transferrin with a low pK a that is elevated upon binding of sulphate

FEBS Letters

Clarkson, John¹  Smith, D.Alastair¹ 

[1] Department of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK

关键词: Transferrin;    Anion binding;    Ultraviolet resonance Raman spectroscopy;    Tyrosinate;    hTf;    human serum transferrin;    apohTf;    apo-human serum transferrin;    hTf/2N;    recombinant N-lobe human serum transferrin;   

DOI  :  10.1016/S0014-5793(01)02687-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The binding of sulphate to human serum apo-transferrin has been examined by ultraviolet absorption and ultraviolet resonance Raman difference spectroscopies between pH 6.0 and 9.0. The ultraviolet absorption data reveals a negative feature at 245 nm that increases in magnitude with pH, with an apparent pK _a of 7.57, which the Raman difference data reveals to be due to tyrosine. The pK _a of this tyrosine is unusually low and is measured at 7.84 by the Raman difference method and is elevated to greater than 9.0 upon addition of sulphate. Previous studies on the N-lobe imply that Tyr 188 is the tyrosine with a low pK _a and also that Arg 124 is the primary binding site for the sulphate. The functional relevance may be that with sulphate bound, both carbonate binding and the deprotonation of Tyr will be disfavoured, and as a result so is iron binding.

【 授权许可】

Unknown