ULTRA-HIGH RESOLUTION STRUCTURES OF THE SRP GTPASE AND ITS HETERODIMERIC RECEPTO

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This proposal has two aims: the first is completion of ultra-high resolution data collection from the GDP and GMPPNP complexes of the SRP GTPase, Ffh, from Thermus aquaticus. These structures, with data from crystals of the apo protein previously collected at SSRL, will form the basis for a comparitive analysis of the structural states of Ffh at ultra-high resolution. Although a member of the GTPase superfamily, the SRP GTPase exhibits a number of novel properties that we aim to understand at a protein structural level. In addition, we have estabished preliminary conditions for crystallization of the GTP-dependent complex of the SRP GTPase Ffh with its receptor FtsY, also a GTPase. We anticipate optimization of the crystallization conditions in the near future, and are requesting data collection time in order to determine this structure using MAD. The structure of the Ffh/FtsY NG complex is particularly significant, because it will reveal the structural basis for the molecular 'handshake' that plays a central role in SRP-mediated targeting.