Fig. 7.

Schematic models summarizing TTN5 kinetic GTPase activities and potential localization within cells. (A) Model of the predicted GTPase nucleotide exchange and hydrolysis cycle of TTN5 based on the biochemical investigation. The TTN5 affinity for mGppNHp is 9.2-fold higher than it is for mGDP resulting in fast switching from inactive GDP-loaded to active GTP-loaded form. mGppNHp dissociation is 8-fold faster than GTP hydrolysis, but both processes were much slower than nucleotide association. TTN5 kinetics identified TTN5 as a non-classical GTPase that tends to stay in a GTP-loaded form even under resting conditions. (B) Presumed TTN5 locations within the cell. TTN5 (green square) can be present at the PM similar as FM4-64 (red circle) or in the endomembrane compartments of the TGN or MVB as found by ARA7-colocalization (red hexagon). Additionally, TTN5 might colocalize with GmMan1-positive (red square) Golgi stacks.