The activation cycle of Rab GTPase Ypt32 reveals structural determinants of effector recruitment and GDI binding.
Rab GTPases localize to distinct sub-cellular compartments and regulate vesicle trafficking in eukaryotic cells. Yeast Rabs Ypt31/32 and Sec4 have 68% homology and bind to common interactors, yet play distinct roles in the transport of exocytic vesicles. The structures of Ypt31/32 have not previously been reported in the uncomplexed state. We describe the crystal structures of GTP and GDP forms of Ypt32 to understand the molecular basis for Rab function. The structure of Ypt32(GTP) reveals that the switch II conformation is distinct from Sec4(GTP) in spite of a highly conserved amino acid sequence. Also, Ypt32(GDP) reveals a remarkable change in conformation of the switch II helix induced by binding to GDI, which has not been described previously.
School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland.
Azmiri
A
Sultana
Yui
Y
Jin
Carmen
C
Dregger
Edward
E
Franklin
Lois S
LS
Weisman
Amir R
AR
Khan
D000595:Amino Acid Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000737:chemistry* / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000737:chemistry / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D011487:Protein Conformation; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism; D016415:Sequence Alignment; D020691:rab GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism
D020730:Guanine Nucleotide Dissociation Inhibitors; D029701:Saccharomyces cerevisiae Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; C121633:YPT32 protein, S cerevisiae; C064320:SEC4 protein, S cerevisiae; D020691:rab GTP-Binding Proteins