-  Note that guanyl-nucleotide exchange factor (GEF) activity alters binding affinity, but not GTPase catalytic activity directly. Therefore GO:0005085 is under 'regulation of GTPase activity' but is not a 'GTPase regulator', which is reserved for cases where the action of one gene product directly alters the rate of catalysis by another gene product.
-  GO:0019839
-  molecular_function
-  GO:0008433
- [en] guanyl-nucleotide exchange factor activity
-  GO:0016219