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14
CONTENTS
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© 2002 by CRC Press LLC
Signal Peptides
Kenta Nakai
Abstract..................................................................................................................296
14.1 Brief Retrospection ......................................................................................296
14.2 Protein Secretion Pathways in Bacteria.......................................................297
14.2.1 SecB-Dependent Pathway................................................................298
14.2.1.1 SecB ..................................................................................298
14.2.1.2 SecA..................................................................................299
14.2.1.3 SecYEG and Related Proteins..........................................300
14.2.2 SRP-Dependent Pathway in Bacteria ..............................................300
14.2.2.1 Ffh and 4.55 RNA ............................................................300
14.2.2.2 FtsY...................................................................................301
14.2.3 Tat-Dependent Pathway ...................................................................301
14.2.4 Unknown or Factor-Independent Pathway ......................................302
14.2.4.1 Insertion of Procoat Proteins............................................302
14.2.4.2 Energetic Aspects..............................................................302
14.3 Protein Secretion Pathways in Eukaryotes..................................................303
14.3.1 Cotranslational Pathway...................................................................303
14.3.1.1 Targeting to the ER...........................................................303
14.3.1.2 Translocon Complex.........................................................304
14.3.2 Post-Translational Pathway..............................................................304
14.3.2.1 Additional Membrane Proteins ........................................304
14.3.2.2 Role of Chaperone Proteins .............................................305
14.4 Sequence Features and Specificity ..............................................................305
14.4.1 General Features ..............................................................................305
14.4.1.1 Tripartite Structure............................................................305
14.4.1.2 Signal Anchors..................................................................306
14.4.2 Signal Peptidases..............................................................................306
14.4.2.1 Distribution of Type I Signal Peptidases .........................306
14.4.2.2 Specificity of Type I Signal Peptidases............................307
14.4.2.3 Other Types of Signal Peptidases.....................................307
14.4.3 Determinants of Specificity .............................................................307
14.4.3.1 Eubacterial Signal Peptides ..............................................308
14.4.3.2 Eukaryotic Signal Peptides...............................................309
295