This project will increase interoperability between four ELIXIR resources (CATH, SWISS-MODEL, InterPro and PDBe), three of which are Core Resources, by building APIs that facilitate the import and export of data between them. The ultimate goal is to improve provision of 3D-Models for protein domain sequences via CATH, SWISS-MODEL and InterPro. Less than 10% of known sequences have experimentally characterised 3D structural information and yet this data is often essential for understanding the protein’s molecular function and biological role and for determining whether residue mutations could damage the protein and lead to disease. So this integration is very timely as it will enhance links between sequence and structure data. APIs will be built using well-established protocols and as well as promoting interoperability, and therefore sustainability, we will expand the data in each resource to ensure they serve a wider community of biologists.