|
||
J. Cell Biol.,
Volume 140, Number 2, January 26, 1998 259-270
Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037
The mammalian guanosine triphosphate
(GTP)ase-activating protein RanGAP1 is the first example of a protein covalently linked to the ubiquitin-related protein SUMO-1. Here we used peptide mapping, mass spectroscopy analysis, and mutagenesis to
identify the nature of the link between RanGAP1 and
SUMO-1. SUMO-1 is linked to RanGAP1 via glycine
97, indicating that the last 4 amino acids of this 101-
amino acid protein are proteolytically removed before its attachment to RanGAP1. Recombinant SUMO-1
lacking the last four amino acids is efficiently used for
modification of RanGAP1 in vitro and of multiple unknown proteins in vivo. In contrast to most ubiquitinated proteins, only a single lysine residue (K526) in
RanGAP1 can serve as the acceptor site for modification by SUMO-1. Modification of RanGAP1 with
SUMO-1 leads to association of RanGAP1 with the nuclear envelope (NE), where it was previously shown to
be required for nuclear protein import. Sufficient information for modification and targeting resides in a 25-kD
domain of RanGAP1. RanGAP1-SUMO-1 remains
stably associated with the NE during many cycles of in
vitro import. This indicates that removal of RanGAP1 from the NE is not a required element of nuclear protein import and suggests that the reversible modification of RanGAP1 may have a regulatory role.
This article has been cited by other articles:
|
|