.. A Guide to the Genetics of ..

                    .. Leber's Hereditary Optic Neuropathy 'LHON' ..

                              .. a Mitochondrial Disorder of the Enzyme 'Complex I' ..


Complex I is the largest enzyme in the mitochondrial oxidatative phosphorylation system (OXPHOS) and is made up of 44 subunits. 7 of the subunits are encoded by genes on the mtDNA - ND1, ND2, ND3, ND4, ND4L, ND5, ND6 and the remainder by genes on the chromosomes. The purpose of the enzyme is to convert NADH to NAD + H+ and 'pump' the H+ into the inter-membrane space of a mitochondrion. The enzyme is L-shaped with a hydrophilic 'upper' arm concerned with the oxidation of NADH, and a 'lower' hydrophobic arm which is made up of the mtDNA transmembrane subunits and 'pumps' protons into the inter-membrane space.                     Complex I

                    Complex I