The design and structural characterization of oligomeric beta beta alpha mini-proteins
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004.
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| Format: | Thesis |
| Language: | eng |
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Massachusetts Institute of Technology
2005
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| Online Access: | http://hdl.handle.net/1721.1/17737 |
| _version_ | 1811086725704843264 |
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| author | Ali, Mayssam H. (Mayssam Hani), 1976- |
| author2 | Barbara Imperiali. |
| author_facet | Barbara Imperiali. Ali, Mayssam H. (Mayssam Hani), 1976- |
| author_sort | Ali, Mayssam H. (Mayssam Hani), 1976- |
| collection | MIT |
| description | Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004. |
| first_indexed | 2024-09-23T13:33:01Z |
| format | Thesis |
| id | mit-1721.1/17737 |
| institution | Massachusetts Institute of Technology |
| language | eng |
| last_indexed | 2024-09-23T13:33:01Z |
| publishDate | 2005 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/177372019-04-12T14:29:56Z The design and structural characterization of oligomeric beta beta alpha mini-proteins Ali, Mayssam H. (Mayssam Hani), 1976- Barbara Imperiali. Massachusetts Institute of Technology. Dept. of Chemistry. Massachusetts Institute of Technology. Dept. of Chemistry. Chemistry. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004. Vita. Includes bibliographical references. Oligomeric mini-proteins, short peptides with protein-like features, constitute valuable minimal models for the study of oligomeric proteins. Oligomerization is a common feature of cellular proteins that may confer structural and functional advantages. Oligomerization is proposed to have arisen by several evolutionary pathways. The structural characterization of peptide 1, a stable oligomeric mini-protein previously developed in the Imperiali group, was undertaken by X-ray crystallography, as knowledge of the structure would enable the rational design of subsequent generations of BBA oligomers varying in packing and stoichiometry. The structure of peptide 1 could not be solved by direct methods, by molecular replacement with search models derived from the monomeric precursor, or by the introduction of heavy atoms. Two selenomethionine mutants having solution-phase properties comparable to the native were identified. The structures of these two peptides were independently solved via MAD phasing experiments, and the refined structures employed as search models for a molecular replacement solution of 1. The structures of the three peptides are homologous, and constitute the first reported structures of a mixed act/ oligomeric mini-protein. The X-ray crystal structures reveal that the oligomeric BBA motif has a domain-swapped architecture that supports a protein-like and water-exclusive core. The structures elucidate the unique role of unnatural amino acids in conferring native secondary structure in a short peptide sequence (21 residues per monomer). (cont.) Furthermore, the crystal structures reveal that the stoichiometry of the oligomer is tetrameric, rather than trimeric, as originally proposed. A tetrameric solution-phase stoichiometry for this mini-protein family was confirmed by rigorous analytical ultracentrifugation experiments. Heterooligomeric BBA peptides have been designed and characterized in collaboration with Christina M. Taylor and Professor Amy E. Keating of the MIT Biology Department. Acidic and basic residues were substituted along the inter-monomer interface and specific steric interactions were designed in order to disfavor homoassociation and favor heteroassociation. Heterotetramers comparable to peptide 1 in terms of structure and stoichiometry, and approaching the native homotetramer in terms of stability, have been characterized by a variety of biophysical techniques. by Mayssam H. Ali. Ph.D. 2005-06-02T18:27:08Z 2005-06-02T18:27:08Z 2004 2004 Thesis http://hdl.handle.net/1721.1/17737 56481044 eng M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 203 leaves 7351384 bytes 7351191 bytes application/pdf application/pdf application/pdf Massachusetts Institute of Technology |
| spellingShingle | Chemistry. Ali, Mayssam H. (Mayssam Hani), 1976- The design and structural characterization of oligomeric beta beta alpha mini-proteins |
| title | The design and structural characterization of oligomeric beta beta alpha mini-proteins |
| title_full | The design and structural characterization of oligomeric beta beta alpha mini-proteins |
| title_fullStr | The design and structural characterization of oligomeric beta beta alpha mini-proteins |
| title_full_unstemmed | The design and structural characterization of oligomeric beta beta alpha mini-proteins |
| title_short | The design and structural characterization of oligomeric beta beta alpha mini-proteins |
| title_sort | design and structural characterization of oligomeric beta beta alpha mini proteins |
| topic | Chemistry. |
| url | http://hdl.handle.net/1721.1/17737 |
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