The interaction of Citrate-capped gold nanoparticles (AuNPs) with Bovine gamma globulin (BGG) was studied using Fourier transform infrared (FTIR), UV-Visible and Fluorescence spectroscopy. FTIR has confirmed the conjugation of AuNPs and BGG. Fluorescence quenching of tryptophan has confirmed the strong interaction between BGG and AuNPs. UV-Visible and Fluorescence spectroscopy have investigated the extent of interaction by determining the binding constants. Binding constants evaluated from UV-Visible and Fluorescence data are in good agreement with each other. An independent class of binding site on BGG for AuNPs has been predicted, where AuNPs interact with a highly solvent accessible tryptophan residue.