Atypical Switch-I Arginine plays a catalytic role in GTP hydrolysis by Rab21 from Entamoeba histolytica

• Published in: Biochemical and biophysical research communications 2018-11, Vol.506 (3), p.660-667
• Main Authors: Kotyada, Chaithanya, Chandra, Mintu, Tripathi, Aashutosh, Narooka, Anil R., datta, Sunando, Verma, Akash
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; Amino Acid Motifs; Amino Acid Sequence; AMOEBA; ARGININE; Arginine - metabolism; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Binding Sites; Biocatalysis; Entamoeba histolytica - metabolism; GLUTAMINE; Glutamine - metabolism; Guanosine Triphosphate - metabolism; HYDROLYSIS; Intrinsic GTP hydrolysis; Kinetics; LIVER; Models, Molecular; Mutant Proteins - metabolism; Protein Binding; rab GTP-Binding Proteins - chemistry; rab GTP-Binding Proteins - metabolism; Rab GTPase; Structure-Activity Relationship; Switch-I; Switch-II
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2018.10.113

Entamoeba histolytica, the causative agent of amoebic dysentery, liver abscess and colitis, exploits its vesicular trafficking machinery for survival and virulence. Rab family of small GTPases play a key role in the vesicular transport by undergoing the GTP/GDP cycle which is central to the biological processes. Amoebic genome encodes several atypical Rab GTPases which are unique due to absence of conserved sequence motif(s) or atypical residues in their catalytic site [Saito-Nakano et al., 2005 ]. Previously, EhRab21 has been reported to involve in amoebic invasion and migration [Emmanuel et al., 2015 ]. The conserved Glutamine of switch-II region is universally accepted to be crucial for GTP hydrolysis. Mutations that reduce the sidechain polarity of Glutamine render the protein GTPase activity deficient [Krengel et al., 1990]. Here, we report a catalytic role of atypical switch-I Arginine (R36) in intrinsic GTP hydrolysis catalysed by EhRab21. Unlike the GTPase activity deficient QL mutants, the GTPase activity of EhRab21Q64L was found to be marginally enhanced compared to the wild-type protein. Although EhRab21R36L mutant showed normal GTPase activity, the double mutant (R36L/Q64L) was found to be GTPase deficient. Thus, EhRab21 is a unique member of small GTPase family in which an atypical switch-I Arginine is capable of driving GTP hydrolysis independent of the conserved switch-II Glutamine.