Skip Navigation


MBE Advance Access originally published online on October 1, 2003
This Article
Right arrow Full Text Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow Supplementary Material
Right arrow All Versions of this Article:
21/1/97    most recent
msg244v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrow Search for citing articles in:
ISI Web of Science (1)
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Fornasari, M. S.
Right arrow Articles by Echave, J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Fornasari, M. S.
Right arrow Articles by Echave, J.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

Mol. Biol. Evol. 21(1):97-107. 2004
DOI: 10.1093/molbev/msg244
© 2004 by the Society for Molecular Biology and Evolution. ISSN: 0737-4038

Sequence Determinants of Quaternary Structure in Lumazine Synthase

María Silvina Fornasari*,1, Diego A. Laplagne{dagger}, Nicolás Frankel{ddagger}, Ana A. Cauerhff{dagger}, Fernando A. Goldbaum{dagger} and Julián Echave*,1

* Universidad Nacional de Quilmes, Bernal, Argentina
{dagger} Fundación Instituto Leloir (IIBBA-CONICET, IIB-FCEN-UBA), Buenos Aires, Argentina
{ddagger} Laboratorio de Fisiología y Biología Molecular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina

E-mail: silvina{at}unq.edu.ar.; je{at}unq.edu.ar.

Riboflavin, an essential cofactor for all organisms, is biosynthesized in plants, fungi and microorganisms. The penultimate step in the pathway is catalyzed by the enzyme lumazine synthase. One of the most distinctive characteristics of this enzyme is that it is found in different species in two different quaternary structures, pentameric and icosahedral, built from practically the same structural monomeric unit. In fact, the icosahedral structure is best described as a capsid of twelve pentamers. Despite this noticeable difference, the active sites are virtually identical in all structurally studied members. Furthermore, the main regions involved in the catalysis are located at the interface between adjacent subunits in the pentamer. Thus, the two quaternary forms of the enzyme must meet similar structural requirements to achieve their function, but, at the same time, they should differ in the sequence traits responsible for the different quaternary structures observed.

Here, we present a combined analysis that includes sequence-structure and evolutionary studies to find the sequence determinants of the different quaternary assemblies of this enzyme. A data set containing 86 sequences of the lumazine synthase family was recovered by sequence similarity searches. Seven of them had resolved three-dimensional structures. A subsequent phylogenetic reconstruction by maximum parsimony (MP) allowed division of the total set into two clusters in accord with their quaternary structure. The comparison between the patterns of three-dimensional contacts derived from the known three-dimensional structures and variation in sequence conservation revealed a significant shift in structural constraints of certain positions. Also, to explore the changes in functional constraints between the two groups, site-specific evolutionary rate shifts were analyzed.

We found that the positions involved in icosahedral contacts suffer a larger increase in constraints than the rest. We found eight sequence sites that would be the most important icosahedral sequence determinants. We discuss our results and compare them with previous work. These findings should contribute to refinement of the current structural data, to the design of assays that explore the role of these positions, to the structural characterization of new sequences, and to initiation of a study of the underlying evolutionary mechanisms.

Key Words: lumazine synthase • quaternary structure • structural constraints • evolutionary rates


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?


This article has been cited by other articles:


Home page
 Mol. Cell. ProteomicsHome page
J.-B. Peltier, Y. Cai, Q. Sun, V. Zabrouskov, L. Giacomelli, A. Rudella, A. J. Ytterberg, H. Rutschow, and K. J. van Wijk
The Oligomeric Stromal Proteome of Arabidopsis thaliana Chloroplasts
Mol. Cell. Proteomics, January 1, 2006; 5(1): 114 - 133.
[Abstract] [Full Text] [PDF]


Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.