Human ORC1 homology model. Left panel shows the ORCI model, created as dcflbed in , viewedfroni the cytoplasnijc side ith the substrate-binding site containing L- ornithine. The central panel shows the location of the mutations causing the H H H syndrome in the ORC1 model viewed as in the left panel but displayed with residues close to the binding site colored in cyan, residues close to the substrate exit/entrance on the cytosolic side in green and residues close to the substrate exit/entrance on the matrix side in magenta. The right panel shows the ORC1 model. viewed from the membrane side with the color scheme as in the central panel.