Electronic Thesis and Dissertation Repository


Master of Science




Dr. Stan Dunn


F1Fo ATP synthases are rotary enzymes that produce most ATP in living organisms. The enzymes’ b2δ subunits form a stator stalk that holds the F1 sector against the torque of the rotor. In Escherichia coli, b2 is an asymmetric homodimer. However, ATPases from some species have a heterodimer of subunits b and b’. Here, a modified E. coli ATP synthase containing a heterodimeric stator stalk was engineered by replacing residues 34-110 of E. coli b with sequences of Rhodobacter capsulatus b and b’, and expressing both chimeras. This produced a functional, heterodimeric enzyme useful for investigating the two b subunits through mutation. Then we studied the evolution of b and b’. The heterodimeric system has evolved at least four times, and the gene duplication is usually linked with rearrangement of ATP synthase genes into multiple transcriptional units. Groups with each gene pattern mapped as clades onto a tree of life.

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