4Q6S: CFTR Associated Ligand (CAL) PDZ

CFTR Associated Ligand (CAL) PDZ bound to biotinylated peptide BT-L-iCAL36. Determined by X-ray diffraction at 1.45 Å resolution. Released 29 Apr 2015.

Method: X-ray diffraction
Resolution: 1.45 Å
Organism: Homo sapiens
Chains: 4
Atoms: 1,882
Mol. weight: 22.8 kDa
Released: 29 Apr 2015

Explore 4Q6S in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

4Q6S contains 7 α-helices and 15 β-strands across 4 chains. 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: 3 helices, 6 β-strands

Element	Residues	Length	Sheet
β-strand	287-293	7	1
β-strand	301-306	6	1
α-helix	307-309	3
β-strand	311-318	8	1
α-helix	323-327	5
β-strand	334-339	6	1
β-strand	342-343	2	1
α-helix	349-358	10
β-strand	361-369	9	1

Chain B: 3 helices, 7 β-strands

Element	Residues	Length	Sheet
β-strand	287-292	6	2
β-strand	297	1	1
β-strand	301-306	6	2
α-helix	307-309	3
β-strand	311-318	8	2
α-helix	323-327	5
β-strand	335-339	5	2
β-strand	342-343	2	2
α-helix	349-358	10
β-strand	362-368	7	2

Chain C: 1 helix, 1 β-strand

Element	Residues	Length	Sheet
α-helix	5-7	3
β-strand	12-14	3	1

Chain D: 0 helices, 1 β-strand

Element	Residues	Length	Sheet
β-strand	12-14	3	2

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Golgi-associated PDZ and coiled-coil motif-containing protein	A, B	protein	87	Homo sapiens	Q9HD26 (AlphaFold model)
BT-L-iCAL36 peptide	C, D	protein	16

Sequence of entity 1 (A, B), FASTA

>4Q6S_1 Golgi-associated PDZ and coiled-coil motif-containing protein (chains A, B)
GPIRKVLLLKEDHEGLGISITGGKEHGVPILISEIHPGQPADRCGGLHVGDAILAVNGVN
LRDTKHKEAVTILSQQRGEIEFEVVYV

Sequence of entity 2 (C, D), FASTA

>4Q6S_2 BT-L-iCAL36 peptide (chains C, D)
XWRFKKANSRLPTSII

Primary citation

Sequence Engineering at Non-motif Modulator Residues Yields a Peptide That Effectively Targets a Single PDZ Protein in a Disease-relevant Cellular Context. Amacher, J.F., Cushing, P.R., Vouilleme, L. et al. J Mol Biol (2026) 438:169597-169597. DOI 10.1016/j.jmb.2025.169597 · PubMed

Other PDB entries of the same protein (UniProt Q9HD26 (AlphaFold model), which also has an AlphaFold model), best resolution first:

4JOK 1.09 Å, CFTR Associated Ligand (CAL) PDZ domain bound to peptide Y-iCAL36 (ANSRYPTSII)
4JOE 1.14 Å, CFTR Associated Ligand (CAL) PDZ domain bound to peptide A-iCAL36 (ANSRAPTSII)
4JOF 1.2 Å, CFTR Associated Ligand (CAL) PDZ domain bound to peptide L-iCAL36 (ANSRLPTSII)
4JOJ 1.2 Å, CFTR Associated Ligand (CAL) domain bound to peptide F-iCAL36 (ANSRFPTSII)
4NMP 1.3 Å, CFTR Associated Ligand (CAL) PDZ domain bound to peptide iCAL36(Ac-K-3) (ANSRWP[Ac-K]SII)
4JOR 1.34 Å, CFTR Associated Ligand (CAL) PDZ domain bound to HPV18 E6 oncoprotein C-terminal peptide…
7JZQ 1.35 Å, CFTR Associated Ligand (CAL) PDZ domain bound to peptidomimetic LyCALPMB
5K4F 1.36 Å, CAL PDZ mutant C319A with a peptide
4E34 1.4 Å, Crystal structure of CFTR Associated Ligand (CAL) PDZ domain bound to iCAL36…
4E35 1.4 Å, Crystal structure of CFTR Associated Ligand (CAL) PDZ domain bound to iCAL36-L…
4NMO 1.4 Å, CFTR Associated Ligand (CAL) PDZ domain bound to peptide iCAL36(Ac-K-1)(ANSRWPTS[Ac-K]I)
4NMQ 1.4 Å, CFTR Associated Ligand (CAL) PDZ domain bound to peptide iCAL36(Ac-K-4) (ANSRW[Ac-K]TSII)

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