The MLRQ subunit of mitochondrial NADH-ubiquinone reductase complex I is nuclear [1] and is found in plants [2], insects, fungi and higher metazoans [3]. It appears to act within the membrane and, in mammals, is highly expressed in muscle and neural tissue, indicative of a role in ATP generation [3].

1: Sequences of 20 subunits of NADH:ubiquinone oxidoreductase from bovine heart mitochondria. Application of a novel strategy for sequencing proteins using the polymerase chain reaction. Walker JE, Arizmendi JM, Dupuis A, Fearnley IM, Finel M, Medd SM, Pilkington SJ, Runswick MJ, Skehel JM; J Mol Biol 1992;226:1051-1072. PMID:1518044

2: Stability of barley aleurone transcripts: Dependence on protein synthesis, influence of the starchy endosperm and destabilization by GA3. Aalen RB, Salehian Z, Steinum TM; Physiol Plant 2001;112:403-413. PMID:11473698

3: Tracing the evolution of a large protein complex in the eukaryotes, NADH:ubiquinone oxidoreductase (Complex I). Gabaldon T, Rainey D, Huynen MA; J Mol Biol. 2005;348:857-870. PMID:15843018