Intermembl sp IN-2 Fe/S uO Figure 4-6-1 UQH Figure 14 19 osed structure and membrane topography of mi Mat trix 2 tochondrial complex I (NADH: UQ oxidoreductase) n The complex acts as an NADH-ubiquinone oxidore- ductase, transferring electrons from matrix NADH - to ubiquinone. This transfer involves FMN, fo NADH多 iron-sulfur centers(Nl-N4)and an internal quinone (UQ ) The H/2e ratio is thought to be four two H taken up at the internal quinone site IN-1, N-3, N-4 other two translocated by a poorly defined mecha Fe/S nism(dotted line). The complex is readily bro FMN into two smaller complexes, one of which (blue)is very hydrophobic and contains all of the subunits encoded in the mitochondrion. The other arm of the (600 kDa) lex (purple) protrudes into the matrix and is composed of nucleus-encoded subunitsFigure 4-6-1