PDBsum entry 2jm4

Signaling protein

PDB id: 2jm4

Contents

Protein chain

43 a.a. *

Metals

_CA

* Residue conservation analysis

PDB id:

2jm4

Name:

Signaling protein

Title:

The solution nmr structure of the relaxin (rxfp1) receptor ldla module.

Structure:

Relaxin receptor 1. Chain: a. Fragment: ldl-receptor class a, residues 23-63. Synonym: relaxin family peptide receptor 1, leucine-rich repeat- containing g-protein coupled receptor 7, ldla module. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: rxfp1, lgr7. Expressed in: escherichia coli. Expression_system_taxid: 562. Expression_system_variant: trxb.

NMR struc:

24 models

Authors:

E.J.Hopkins,R.A.D.Bathgate,P.R.Gooley

Key ref:

E.J.Hopkins et al. (2007). The NMR solution structure of the relaxin (RXFP1) receptor lipoprotein receptor class A module and identification of key residues in the N-terminal region of the module that mediate receptor activation. J Biol Chem, 282, 4172-4184. PubMed id: 17148455 DOI: 10.1074/jbc.M609526200

Date:

09-Oct-06 Release date: 12-Dec-06

Protein chain

Q9HBX9  (RXFP1_HUMAN) -  Relaxin receptor 1 from Homo sapiens

Seq: 757 a.a.

Struc: 43 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1074/jbc.M609526200

J Biol Chem 282:4172-4184 (2007)

PubMed id: 17148455

The NMR solution structure of the relaxin (RXFP1) receptor lipoprotein receptor class A module and identification of key residues in the N-terminal region of the module that mediate receptor activation.

E.J.Hopkins, S.Layfield, T.Ferraro, R.A.Bathgate, P.R.Gooley.

ABSTRACT

The receptors for the peptide hormones relaxin and insulin-like peptide 3 (INSL3) are the leucine-rich repeat-containing G-protein-coupled receptors LGR7 and LGR8 recently renamed as the relaxin family peptide (RXFP) receptors, RXFP1 and RXFP2, respectively. These receptors differ from other LGRs by the addition of an N-terminal low density lipoprotein receptor class A (LDLa) module and are the only human G-protein-coupled receptors to contain such a domain. Recently it was shown that the LDLa module of the RXFP1 and RXFP2 receptors is essential for ligand-stimulated cAMP signaling. The mechanism by which the LDLa module modulates receptor signaling is unknown; however, it represents a unique paradigm in understanding G-protein-coupled receptor signaling. Here we present the structure of the RXFP1 receptor LDLa module determined by solution NMR spectroscopy. The structure is similar to other LDLa modules but shows small differences in side chain orientations and inter-residue packing. Interchange of the module with the second ligand binding domain of the LDL receptor, LB2, results in a receptor that binds relaxin with full affinity but is unable to signal. Furthermore, we demonstrate via structural studies on mutated LDLa modules and functional studies on mutated full-length receptors that a hydrophobic surface within the N-terminal region of the module is essential for activation of RXFP1 receptor signal in response to relaxin stimulation. This study has highlighted the necessity to understand the structural effects of single amino acid mutations on the LDLa module to fully interpret the effects of these mutations on receptor activity.

Selected figure(s)

Figure 1.
FIGURE 1. A, stereo view of the ensemble of the 24 lowest energy structures of the RXFP1 receptor LDLa module. B, ribbon representation of the RXFP1 receptor LDLa module. -Strands are colored aqua and the 3[10] helix red/yellow. C, overlay of the RXFP1 receptor LDLa module on the x-ray crystal structure of LB5. The r.m.s.d. of the overlay is 1.9 Å. Although not represented by MOLMOL, NOE data suggest that there is a second 3[10] helix in the C-terminal region of RXFP1 LDLa as seen in the LB5 structure. D, comparison of side chain orientation of Phe-10 in relation to LB5. The side chains of RXFP1 LDLa are blue and those of LB5 are red. Both phenylalanine residues pack against an unconserved residue; however, the [1] of the RXFP1 Phe-10 is +60, whereas in LB5 and other LDLa modules it is +180. E, overlay of residues that bind the calcium ion necessary for structure. Residues of the RXFP1 LDLa module are colored blue and LB5 red. Numbering is by the RXFP1 sequence.

Figure 3.
FIGURE 3. RP-HPLC profiles of GB1-LDLa and variants. The top elution profile is of the protein oxidized in the presence of 2.5 mM CaCl[2]. The second profile is the protein oxidized in the absence of calcium chloride and in the presence of 1 mM EDTA. The third profile is the unfolded protein in the presence of 1 mM dithiothreitol (DTT). GB1-LDLa L7A and GB1-LDLa L22 generate elution profiles very similar to the wild type protein that elutes as a single peak when oxidized in the presence of calcium or as multiple peaks when oxidized in the presence of EDTA. Refolding of GB1-LDLa Y9A, GB1-LDLa F10A, and GB1-LDLa L23A appears to be disrupted by each mutation, as the proteins oxidized in the presence of calcium elute as several peaks. The fraction collected that appeared to be folded by NMR is indicated with shading and an arrow. The other fractions collected were assessed as unfolded by NMR.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2007, 282, 4172-4184) copyright 2007.

Figures were selected by an automated process.