Core subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I) that is believed to belong to the minimal assembly required for catalysis. Complex I functions in the transfer of electrons from NADH to the respiratory chain. The immediate electron acceptor for the enzyme is believed to be ubiquinone (By similarity). NADH-ubiquinone oxidoreductase chain 4L MTND4L NU4LM_HORSE ND4L 98 NADH4L MSLVHINIFLAFTVSLVGLLMYRSHLMSSLLCLEGMMLSLFVMATMMVLNTHFTLASMMPIILLVFAACERALGLSLLVMVSNTYGVDHVQNLNLLQC MT-ND4L NADH dehydrogenase subunit 4L