CHAPTER 6
 CONCLUSIONS AND FUTURE DIRECTIONS

 Conclusions

 The work presented in the preceding chapters had a considerable impact on the way

the b2 homodimer of the E. coli F1Fo ATP synthase is viewed and may provide some

implications concerning the genetically dissimilar b-type subunit heterodimers found in

higher organisms. A previous analysis of the b subunit performed in Dr. Cain's

laboratory had suggested that the b2 dimer has a flexible characteristic in its tether region

(193, 194). A two plasmid expression system novel to the studies of the E. coli b subunit

was developed in Chapter 2 in order to determine if the apparent flexibility extended to

the dimerization of the b subunit. This work provided interesting information concerning

the tether region of the peripheral stalk. The two plasmid expression system was also

utilized in Chapter 3 to study the function of individual b subunits in the peripheral stalk

by exploiting b subunits with known defective mutations. From this work, a model has

been developed concerning the positioning of the two b subunits relative to the F1Fo ATP

synthase complex and the intersubunit contacts made by the individual b subunits. On

another note, Chapter 4 describes single cysteine substitutions that were generated in

different length b subunits with the ultimate goal of studying the apparent flexibility of

the b2 dimer. And finally, Chapter 5 describes mutagenesis work performed on the

extreme amino- and carboxyl-termini of the b2 dimer in contribution to ongoing

experiments performed by others in the laboratory. The following sections will

summarize and discuss the implications of the results from Chapters 2, 3, 4 and 5 and