9RFF: Human Rac1 Fused with the Scaffold Protein POSH

Crystal Structure of Human Rac1 Fused with the Scaffold Protein POSH (residues 319-371). Determined by X-ray diffraction at 1.25 Å resolution. Released 3 Dec 2025.

Method: X-ray diffraction
Resolution: 1.25 Å
Organism: Homo sapiens
Chains: 1
Atoms: 1,958
Mol. weight: 26.23 kDa
Ligands: GNP, MG
Released: 3 Dec 2025

Explore 9RFF in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9RFF contains 13 α-helices and 10 β-strands across 1 chain. Residue ranges use author residue numbering, as in the PDB file, from PDBe. To see them in 3D, choose the Cartoon representation with Secondary structure coloring: helices, sheets and coils get different colors.

Chain A: 13 helices, 10 β-strands

Element	Residues	Length	Sheet
β-strand	2-10	9	1
α-helix	16-25	10
β-strand	37-46	10	1
β-strand	49-58	10	1
α-helix	62-64	3
α-helix	68-71	4
β-strand	77-83	7	1
α-helix	87-92	6
α-helix	93-97	5
α-helix	98-104	7
β-strand	110-115	6	1
α-helix	117-119	3
α-helix	123-131	9
α-helix	136-138	3
α-helix	139-148	10
β-strand	153-156	4	1
α-helix	165-176	12
β-strand	326	1	1
α-helix	327-329	3
β-strand	330-334	5	1
α-helix	337-344	8
β-strand	356-360	5	2
β-strand	363-367	5	2

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Ras-related C3 botulinum toxin substrate 1,E3 ubiquitin-protein ligase SH3RF1	A	protein	233	Homo sapiens	P63000 (AlphaFold model), Q7Z6J0 (AlphaFold model)

Sequence of entity 1 (A), FASTA

>9RFF_1 Ras-related C3 botulinum toxin substrate 1,E3 ubiquitin-protein ligase SH3RF1 (chains A)
GRRMQAIKCVVVGDGAVGKTCLLISYTTNAFPGEYIPTVFDNYSANVMVDGKPVNLGLWD
TAGQEDYDRLRPLSYPQTDVFLICFSLVSPASFENVRAKWYPEVRHHCPNTPIILVGTKL
DLRDDKDTIEKLKEKKLTPITYPQGLAMAKEIGAVKYLECSALTQRGLKTVFDEAIRAVL
QNRHSMEISPPVLISSSNPTAAARISELSGLSCSAPSQVHISTTGLIVTPPPS

Ligands and cofactors

ID	Name	Formula	Copies
GNP	Phosphoaminophosphonic acid-guanylate ester	C10 H17 N6 O13 P3	1
MG	Magnesium ion	Mg	1

Water and common crystallization additives (MPD) are not listed.

Primary citation

Hierarchical folding-upon-binding of an intrinsically disordered protein. Kjaer, L.F., Ielasi, F.S., Winbolt, T. et al. Nat Commun (2025) 16:11346-11346. DOI 10.1038/s41467-025-66420-5 · PubMed

Other PDB entries of the same protein (UniProt P63000 (AlphaFold model), which also has an AlphaFold model), best resolution first:

9IFK 1.34 Å, Crystal structure of Kalirin/Rac1 in complex with DK-2
1MH1 1.38 Å, Small G-protein
9HU8 1.48 Å, Crystal structure of Kalirin/Rac1 in complex with MC-278.
2WKQ 1.6 Å, Structure of a photoactivatable Rac1 containing the Lov2 C450A Mutant
6X1G 1.6 Å, Crystal structure of a GEF domain from the Orientia tsutsugamushi protein OtDUB in…
5O33 1.64 Å, A structure of the GEF Kalirin DH1 domain in complex with the small GTPase Rac1
9IG1 1.65 Å, Crystal structure of Kalirin/Rac1 in complex with DK-652
9I1L 1.68 Å, Crystal structure of Kalirin/Rac1 in complex with RS-009
8I5V 1.73 Å, DOCK10 mutant L1903Y complexed with Rac1
1RYF 1.75 Å, Alternative Splicing of Rac1 Generates Rac1b, a Self-activating GTPase
1RYH 1.75 Å, Alternative Splicing of Rac1 Generates Rac1b, a Self-activating GTPase
9TJY 1.77 Å, Crystal Structure of the Human Oncogenic Splice Variant Rac1b Fused with the Scaffold…

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