1H, 15N and 13C Resonance assignments and secondary structure determination reveal that the minimal Rac1 GTPase binding domain of plexin-B1 has a ubiquitin fold.

Semaphorin molecules serve as axon guidance signals that regulate the navigation
of neuronal growth cones. Semaphorins have also been implicated in other
biological processes, including the immune response. Plexins, acting either
alone or in complex with neuropilins, have recently been identified as
functional semaphorin receptors. However, the mechanisms of signal transduction
by plexins remain largely unknown. We have demonstrated a direct interaction
between plexin-B1 and activated Rac. Rac specifically interacts with the
cytosolic domain of plexin-B1, but not with that of plexin-A3 or -C1. Neither
RhoA nor Cdc42 interacts with plexin-B1, indicating that the Rac/plexin-B1
interaction is highly specific. The binding of GTP and the integrity of the Rac
effector domain are required for the interaction with plexin-B1. Furthermore,
we have identified that a Cdc42/Rac interactive binding (CRIB) motif in the
cytosolic domain of plexin-B1 is essential for its interaction with active Rac.
We have also observed that the semaphorin CD100, a ligand for plexin-B1,
stimulates the interaction between plexin-B1 and active Rac. Our results
support a model by which activated Rac plays a role in mediating semaphorin
signals, resulting in reorganization of actin cytoskeletal structure.

Vikis HG, Li W, He Z, Guan KL.
Proc Natl Acad Sci U S A. 2000 Nov 7;97(23):12457-62.

Proceedings of the National Academy of Sciences of the United States of America
The semaphorin receptor plexin-B1 specifically interacts with active Rac in a ligand-dependent manner.

Nmr Solution Structure Of The Rho Gtpase Binding Domain Of Human Plexin-B1

Crystal Structure Of The Effector Domain Of Human Plexin B1

Crystal Structure Of The Effector Domain Of Plxnb1 Bound With Rnd1 Gtpase

Crystal Structure Of The Cytoplasmic Domain Of Human Plexin B1

Crystal Structure Of A Truncated Intracellular Domain Of Plexin-B1 In Complex With Rac1

Crystal Structure Of The Intracellular Domain Of Plexin-B1 In Complex With Rac1

plexin-B1 precursor [synthetic construct]

PREDICTED: LOW QUALITY PROTEIN: plexin-B1 [Nomascus leucogenys]

PREDICTED: plexin-B1 isoform X2 [Saimiri boliviensis boliviensis]

PREDICTED: plexin-B1 isoform 1 [Gorilla gorilla gorilla]

RecName: Full=Plexin-B1; AltName: Full=Semaphorin receptor SEP; Flags: Precursor [Homo sapiens]

1H, 15N and 13C Resonance Assignments and Secondary Structure Determination
Reveal that the Minimal Rac1 GTPase Binding Domain of Plexin-B1 Has a Ubiquitin
Fold