Protein annotation of the human A2a adenosine receptor. On the left, part of a paper by Gao et al.  is shown; annotated concepts are highlighted in red by pressing the space-bar. On the right, annotation for the A2a receptor (obtained by clicking on the words indicated by the grey arrow) is shown. The protein identifier and family are linked to the protein detail and protein family pages in GPCRDB, respectively. In addition, links to a number of external resources are provided. An image of the protein structure (PDB code 3EML) is shown. Although not annotated in the text, the species mentioned (human, murine, bovine, rat) are used internally for protein normalisation.