The function of ENSG00000171204 (TMEM126B, transmembrane protein 126B) is as follows. As part of the MCIA complex, involved in the assembly of the mitochondrial complex I (PubMed:27374773, PubMed:27374774, PubMed:32320651). Participates in constructing the membrane arm of complex I (PubMed:24191001). {ECO:0000269|PubMed:24191001, ECO:0000269|PubMed:27374773, ECO:0000269|PubMed:27374774, ECO:0000269|PubMed:32320651}.