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X‐ray structure of the T. Aquaticus Ftsy:GDP complex suggests functional roles for the C‐terminal helix of the SRP GTPases
Author(s) -
GawronskiSalerno Joseph,
Coon V John S.,
Focia Pamela J.,
Freymann Douglas M.
Publication year - 2007
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.21200
Subject(s) - signal recognition particle , gtpase , signal recognition particle receptor , biology , biophysics , helix (gastropod) , protein targeting , microbiology and biotechnology , biochemistry , peptide sequence , membrane protein , signal peptide , membrane , gene , ecology , snail
FtsY and Ffh are structurally similar prokaryotic Signal Recognition Particle GTPases that play an essential role in the Signal Recognition Particle (SRP)‐mediated cotranslational targeting of proteins to the membrane. The two GTPases assemble in a GTP‐dependent manner to form a heterodimeric SRP targeting complex. We report here the 2.1 Å X‐ray structure of FtsY from T. aquaticus bound to GDP. The structure of the monomeric protein reveals, unexpectedly, canonical binding interactions for GDP. A comparison of the structures of the monomeric and complexed FtsY NG GTPase domain suggests that it undergoes a conformational change similar to that of Ffh NG during the assembly of the symmetric heterodimeric complex. However, in contrast to Ffh, in which the C‐terminal helix shifts independently of the other subdomains, the C‐terminal helix and N domain of T. aquaticus FtsY together behave as a rigid body during assembly, suggesting distinct mechanisms by which the interactions of the NG domain “module” are regulated in the context of the two SRP GTPases. Proteins 2007. © 2006 Wiley‐Liss, Inc.