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. Author manuscript; available in PMC: 2009 Sep 5.
Published in final edited form as: J Mol Biol. 2008 May 29;381(3):581–593. doi: 10.1016/j.jmb.2008.05.049

Figure 1. SRP and SR can form a complex independently of GTP.

Figure 1

(a) Position of FRET donor (●) and acceptor (●) probes on the SRP (Ffh) and SR (FtsY) on a co-crystal structure of the Ffh•FtsY complex 16. (b) Fluorescence emission spectrum of SRP•SR complex in the presence of 100 µM GppNHp. 0.5 µM SRP and 2 µM SR were incubated for 10 minutes at 25 °C to form the SRP•SR complex (red). SRP- and SR-only spectra (green and blue, respectively) were obtained by incubating fluorescently labeled SRP (or SR) with unlabeled SR (or SRP). (c) Fluorescence emission spectrum of SRP•SR complex in the absence of GppNHp. 5 µM SRP and 15 µM SR were incubated at 25 °C for 10 minutes. SRP or SR-only spectra were obtained as in part (b).