 Multible isoforms of the proteins are known due to alternative splicing.The major isoform (isoform 1) is most highly expressed in the liver whereas isoform 2 is found in energy-demanding tissues including the brain, heart, and skeletal muscle.Structure of the HMGCL protein has been resolved by X-ray crystallography at 2.1-Å resolution, and reveals that the protein may function as a dimer.