Size of GFP protein?

Roger Y. Tsien rtsien at UCSD.EDU
Thu Feb 20 20:02:52 EST 1997

At 07:22 PM 2/20/97 -0000, you wrote:
>  Probably something of a trivial question, but is there any discrepancy
>in the estimated size of wild type (or even S65T) GFP? It's just that most
>papers cite it's *estimated* size at around 28kD, but in the Ormo paper on
>GFP structure, mass spec. data gave a figure around 31kD. For what it's
>worth, on our SDS-PAGE gels it runs right with the 31kD marker, but I'm
>not vouching for the accuracy of that at all! 
>   What is the generally held view nowadays?
>     Thanks for any responses,
>     Pete
>Peter Corish
>CRC Chromosome Molecular Biology Group
>Department of Biochemistry
>University of Oxford
>OX1 3QU
>Tel: +44 (0)1865 275222
>Fax: +44 (0)1865 275283

The 31 kDa masses cited in the Ormo et al paper included a polyhistidine
fusion tag, which adds 37 amino acids. Because of space limitations on the
main text, mention of the fusion tag was buried in footnote 18 of that
paper. Without the fusion tag, GFP with the S65T and Q80R mutations is
26,909 Da, pretty close to 27 KDa.
Roger Y. Tsien
rtsien at ucsd.edu
tel. +1(619)534-4891, fax +1(619)534-5270
Howard Hughes Med. Inst., Univ. Calif. San Diego, La Jolla, CA 92093-0647

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