6SRV

Structure of the arginase-2-inhibitory human antigen-binding fragment Fab C0021144

This is a non-PDB format compatible entry.

Summary for 6SRV

• Entry DOI: 10.2210/pdb6srv/pdb
• Related: 6SRX 6SS0 6SS2 6SS3 6SS4 6SS6 6TUL
• Descriptor: Fab C0021144 heavy chain (IgG1), Fab C0021144 light chain (IgG1), CHLORIDE ION, ... (7 entities in total)
• Functional Keywords: arginase-2 inhibitor, igg, antigen-binding fragment, protein binding
• Biological source: Homo sapiens; More
• Total number of polymer chains: 4
• Total formula weight: 97426.74

Authors

Burschowsky, D.,Addyman, A.,Fiedler, S.,Groves, M.,Haynes, S.,Seewooruthun, C.,Carr, M. (deposition date: 2019-09-06, release date: 2020-06-10, Last modification date: 2020-09-16)

Primary citation

Austin, M.,Burschowsky, D.,Chan, D.T.Y.,Jenkinson, L.,Haynes, S.,Diamandakis, A.,Seewooruthun, C.,Addyman, A.,Fiedler, S.,Ryman, S.,Whitehouse, J.,Slater, L.H.,Hadjinicolaou, A.V.,Gileadi, U.,Gowans, E.,Shibata, Y.,Barnard, M.,Kaserer, T.,Sharma, P.,Luheshi, N.M.,Wilkinson, R.W.,Vaughan, T.J.,Holt, S.V.,Cerundolo, V.,Carr, M.D.,Groves, M.A.T.
Structural and functional characterization of C0021158, a high-affinity monoclonal antibody that inhibits Arginase 2 function via a novel non-competitive mechanism of action.
Mabs, 12:1801230-1801230,

PubMed Abstract: Arginase 2 (ARG2) is a binuclear manganese metalloenzyme that catalyzes the hydrolysis of L-arginine. The dysregulated expression of ARG2 within specific tumor microenvironments generates an immunosuppressive niche that effectively renders the tumor 'invisible' to the host's immune system. Increased ARG2 expression leads to a concomitant depletion of local L-arginine levels, which in turn leads to suppression of anti-tumor T-cell-mediated immune responses. Here we describe the isolation and characterization of a high affinity antibody (C0021158) that inhibits ARG2 enzymatic function completely, effectively restoring T-cell proliferation . Enzyme kinetic studies confirmed that C0021158 exhibits a noncompetitive mechanism of action, inhibiting ARG2 independently of L-arginine concentrations. To elucidate C0021158's inhibitory mechanism at a structural level, the co-crystal structure of the Fab in complex with trimeric ARG2 was solved. C0021158's epitope was consequently mapped to an area some distance from the enzyme's substrate binding cleft, indicating an allosteric mechanism was being employed. Following C0021158 binding, distinct regions of ARG2 undergo major conformational changes. Notably, the backbone structure of a surface-exposed loop is completely rearranged, leading to the formation of a new short helix structure at the Fab-ARG2 interface. Moreover, this large-scale structural remodeling at ARG2's epitope translates into more subtle changes within the enzyme's active site. An arginine residue at position 39 is reoriented inwards, sterically impeding the binding of L-arginine. Arg39 is also predicted to alter the p of a key catalytic histidine residue at position 160, further attenuating ARG2's enzymatic function. molecular docking simulations predict that L-arginine is unable to bind effectively when antibody is bound, a prediction supported by isothermal calorimetry experiments using an L-arginine mimetic. Specifically, targeting ARG2 in the tumor microenvironment through the application of C0021158, potentially in combination with standard chemotherapy regimens or alternate immunotherapies, represents a potential new strategy to target immune cold tumors.

PubMed: 32880207
DOI: 10.1080/19420862.2020.1801230

Experimental method

X-RAY DIFFRACTION (2.4 Å)