Metabotropic glutamate receptors (mGluRs) influence a variety of second-messenger systems and ion channels. The C-terminal region of group III mGluRs interacts with the Ca2+-binding protein calmodulin (CaM). We intend to study the interaction between Ca2+/CaM and the CaM-binding motifs within mGluR(7), which is a group III mGluR. We established a recombinant protein expression and purification system for nuclear magnetic resonance (NMR) analysis of mGluR(7) peptides using Escherichia coil. Peptides of mGluR(7) conjugated to an affinity tag sequence were constructed, and protocols for expression and purification were optimized. To suppress non-specific enzymatic cleavage, the mGluR(7) fusion peptide was bound to Ca2+/CaM before enterokinase cleavage. This complex method for precise enzymatic reactions may be applicable for the recombinant preparation of a wide variety of peptides. (C) 2010 Elsevier Inc. All rights reserved.