1. INTRODUCTION 2

2. OVERALL STRUCTURE AND SUBSTRUCTURES 5

2.1 Overall structure and components 5

2.2 Bidirectional rotary motor 5

2.3 Drive shaft 8

2.4 Bushing 8

2.5 Universal joint 9

2.6 Helical propeller 9

2.7 Axial junction 10

2.8 Capping structure 11

3. ASSEMBLY PROCESS OF THE FLAGELLUM 11

3.1 Step by step assembly 11

3.2 Flagellum-specific export apparatus and the channel 12

4. UNIQUE CHARACTERISTICS OF THE FLAGELLAR MOTOR DYNAMICS 13

5. STRUCTURAL DESIGN OF FLAGELLIN FOR ASSEMBLY REGULATION AND POLYMORPHISM 14

5.1 Domain organization and terminal disorder of flagellin 15

5.2 The role of terminal disorder in filament formation and polymorphism 17

5.3 Common structural motif for regulation of self-assembly 21

6. STRUCTURAL DESIGN OF FLAGELLAR FILAMENTS FOR POLYMORPHISM 22

6.1 Polymorphic mechanism 23

6.2 Structures of the filaments deduced by electron microscopy 25

6.2.1 Overview of the electron microscopic studies 25

6.2.2 Helical image reconstruction procedure 27

6.2.3 Structural details of the filament 28

6.3 X-ray fibre diffraction studies 32

6.3.1 Overview of the X-ray studies 32

6.3.2 Orientation of liquid crystalline sols and diffraction patterns 33

6.3.3 Equatorial analysis 35

6.3.4 A preliminary map refined at 11 resolution 37

6.4 Overall chain folding of the subunit in the filament 38

6.4.1 Mapping out the terminal and central regions 38

6.4.2 The chain folding and role of each domain 42

6.5 Polymorphic nature of flagellar filament 43

6.5.1 Comparison of the L- and R-type 43

6.5.2 New helical symmetry Lt-type 46

6.5.3 Direct comparison of the Lt-type lattice to the other two 48

6.5.4 Plausible conformational changes involved in polymorphism 51

7. PERSPECTIVE 55

8. ACKNOWLEDGEMENTS 55

9. REFERENCES 55