Subunit composition of respiratory chain complex 1 and its responses to oxygen in mitochondria from human donor livers

OBJECTIVE: Donor liver function in transplantation is defined by mitochondrial function and the ability of mitochondria to recover from the sequence of warm and/or cold ischemia. Mitochondrial resilience maybe related to assembly and- subunit composition of Complex 1. The aim of this study was to determine if Complex 1 subunit composition was different in donor livers of varying quality and whether oxygen exposure had any effect. RESULTS: Five human livers not suitable for transplant were split. One half placed in cold static storage and the other half exposed to 40% oxygen for 2 h. Protein was extracted for western blot. Membranes were probed with antibodies against β-actin and the following subunits of Complex 1: MTND1, NDUFA10, NDUFB6 and NDUFV2. No difference in steady state Complex 1 subunit composition was demonstrated between donor livers of varying quality, in terms of steatosis or mode of donation. Neither did exposure to oxygen influence Complex 1 subunit composition. This small observational study on subunit levels suggest that Complex 1 is fully assembled as no degradation of subunits associated with the different parts of the enzyme was seen.