Red fluorescent protein eqFP611 and its genetically engineered dimeric variants.
The red fluorescent protein (FP) eqFP611 from the sea anemone Entacmaea quadricolor shows favorable properties for applications as a molecular marker. Like other anthozoan FPs, it forms tetramers at physiological concentrations. The interactions among the monomers, however, are comparatively weak, as inferred from the dissociation into monomers in the presence of sodium dodecyl sulfate (SDS) or at high dilution. Analysis at the single-molecule level revealed that the monomers are highly fluorescent. For application as fusion markers, monomeric FPs are highly desirable. Therefore, we examine the monomer interfaces in the x-ray structure of eqFP611 to provide a basis for the rational design of monomeric variants. The arrangement of the four beta cans is very similar to that of other green fluorescent protein (GFP-like) proteins such as DsRed and RTMS5. A variety of structural features of the tetrameric interfaces explain the weak subunit interactions in eqFP611. We produce functional dimeric variants by introducing single point mutations in the A/B interface (Thr122Arg, Val124Thr). By contrast, structural manipulations in the A/C interface result in essentially complete loss of fluorescence, suggesting that A/C interfacial interactions play a crucial role in the folding of eqFP611 into its functional form.
Wiedenmann
Jörg
J
University of Ulm, Department of Zoology and Endocrinology, 89069 Ulm, Germany. joerg.wiedenmann@biologie.uni-ulm.de
Vallone
Beatrice
B
Renzi
Fabiana
F
Nienhaus
Karin
K
Ivanchenko
Sergey
S
Röcker
Carlheinz
C
Nienhaus
G Ulrich
GU
D000818:Animals; D018360:Crystallography, X-Ray; D005453:Fluorescence; D005818:Genetic Engineering; D014644:Genetic Variation; D008164:Luminescent Proteins / Q000737:chemistry* / Q000235:genetics*; D016297:Mutagenesis, Site-Directed; D020836:Protein Structure, Quaternary; D012615:Sea Anemones
D008164:Luminescent Proteins