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MPRAP: An accessibility predictor for α-helical transmembrane proteins
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.ORCID iD: 0000-0002-7115-9751
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Background:    During the folding of a protein some residues will become exposed to the environmentwhile others will become buried in the protein interior. For water soluble proteins it is en-ergetically favorable to bury hydrophobic residues and expose polar and charged residues tothe surrounding water. However, transmembrane proteins face three distinct environments; ahydrophobic lipid environment inside the membrane, a hydrophilic water environment outsidethe membrane and a interface region rich in phospholipid head-groups. Therefore, for ener-getic reasons the accessible surfaces of transmembrane proteins need to expose different typesof residues at different locations.    Results:    In a set of structurally determined transmembrane proteins it was found that solvent ex-posed residues are quite different inside compared to outside the membrane. In contrast,residues buried within the interior of the protein are much more similar. Further, we foundthat state-of-the-art predictors for surface area are optimized for one of the environments andtherefore perform badly in the other environment. To circumvent this problem we developeda new predictor, MPRAP, that performs well both inside and outside the membrane regions aswell as being better than a combination of specialized predictors. A web-server of MPRAP isavailable at    Conclusion:    By including complete α-helical transmembrane proteins in the training we developed apredictor that accurately predicts accessibility both inside and outside the membrane. This pre-dictor can aid in predicting 3D-structure, predicting functional relevance of individual residuesand identification of erroneous protein structures.

URN: urn:nbn:se:su:diva-35890OAI: diva2:288598
Available from: 2010-01-21 Created: 2010-01-20 Last updated: 2014-11-10Bibliographically approved
In thesis
1. On the effects of structure and function on protein evolution
Open this publication in new window or tab >>On the effects of structure and function on protein evolution
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many proteins can be described as working machines that make sure that everything functions in the cell. Their specific molecular functions are largely dependent on their three-dimensional structures, which in turn are mainly predetermined by their linear sequences of amino acid residues. Therefore, there is a relation between the sequence, structure and function of a protein, in which knowledge about the structure is crucial for understanding the functions. The structure is generally difficult to determine experimentally, but should in principle be possible to predict from the sequence by computational methods. The instructions of how to build the linear proteins sequences are copied during cell division and are passed on to successive generations. Although the copying process is a very efficient and accurate system, it does not function correctly on every occasion. Sometimes errors, or mutations can result from the process. These mutations gradually accumulate over time, so that the sequences and thereby also the structures and functions of proteins evolve overtime. This thesis is based on four papers concerning the relationship between function, structure and sequence and how it changes during the evolution of proteins. Paper I shows that the structural change is linearly related to sequence change and that structures are 3 to 10 times more conserved than sequences. In Paper II and Paper III we investigated non-helical structures and polar residues, respectively, positioned in the nonpolar membrane core environment of α-helical membrane proteins. Both types were found to be evolutionary conserved and functionally important. Paper IV includes the development of a method to predict the residues in α-helical membrane proteins that after folding become exposed to the solvent environment.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2010. 48 p.
protein, structure, function, evolution, membrane
National Category
Biochemistry and Molecular Biology
Research subject
urn:nbn:se:su:diva-35872 (URN)978-91-7155-980-7 (ISBN)
Public defence
2010-02-19, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.Available from: 2010-01-28 Created: 2010-01-20 Last updated: 2014-11-10Bibliographically approved

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Illergård, KristofferElofsson, Arne
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