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Open Access item Estudio termodinámico y estructural del motivo de unión a ADN de HESX-1: relación estabilidad-función en homeodominios
|Authors:||Torrado del Rey, Mario|
|Advisor:||Asensio Álvarez, Juan Luis|
|Keywords:||Homeodominio, Homeodomain, Estabilidad, Stability, Función, Function, Unión a ADN, DNA-binding, Dicroísmo circular, Circular dichroism, Estructura, Structure, ADN, DNA, Proteína, Protein, Termodinámica, Thermodynamic, RMN, NMR, Microcalorimetría, ITC, Puente salino, Salt-bridge|
|Publisher:||Universidad Autónoma de Madrid|
CSIC - Instituto de Química Orgánica General (IQOG)
|Abstract:||Homeodomain proteins are transcription factors present in all eukaryotes and
play key roles in cellular differentiation during development. In fact, mutations
in homeodomain-encoding genes give rise to several inherited diseases in
humans. The homeodomain consists of a 60-residue DNA binding domain
composed of disordered N- and C-terminal regions and three helical segments.
These structural features, together with the highly charged nature of the
polypeptide, determine a typically low stability, property also shared by other
DNA-binding proteins. Conversely, homeodomains usually present a large
DNA-binding affinity. From a molecular recognition perspective, the association
process is sequence-specific and represents an example of the “induced fit”
mechanism. Thus, it has been shown that disordered regions of the protein
become structured upon complex formation, which highlights the relevance of
the protein flexibility in this process. Herein we have investigated the relations
between stability and DNA-binding in the human HESX-1 homeodomain.
The sequence information available for homeodomains reveals that salt
bridges connecting pairs 19-30, 31-42, and 17-52 are frequent, whereas
aliphatic residues at these sites are rare and mainly restricted to proteins from
homeotherms. We have analyzed the influence of salt and hydrophobic bridges
at these sites on the stability and DNA-binding properties of human HESX-1
homeodomain. Regarding the protein stability, our analysis shows that hydrophobic
side chains are clearly preferred at positions 19-30 and 31-42. This
stabilizing influence results from the more favourable packing of the aliphatic
side chains with the protein core, as illustrated by the three-dimensional
solution structure of a thermostable variant, herein reported. In contrast, only
polar side chains seem to be tolerated at positions 17-52. Interestingly, despite
the significant influence of pairs 19-30 and 31-42 on the stability of the
homeodomain, their effect on DNA binding ranges from modest to negligible.
In other words, this analysis reveals an intriguing lack of correlation between
binding strength and the homeodomain conformational stability. Previous
studies have shown that the induced fit of the protein disordered regions plays a key role in the molecular recognition process. On the contrary, according to
our data, the potential adjustment of the structured core of the protein seems
to have little influence on the complex stability. This features might allow and
independent modulation of stability and DNA-binding by evolution.|
|Description:||Parte de los resultados obtenidos en este trabajo
se recogen en el siguiente artículo:
Torrado, M., Revuelta, J., Gonzalez, C., Corzana, F., Bastida, A., Asensio, J.L., 2009.
Role of conserved salt bridges in homeodomain stability and DNA binding.
The Journal of Biological Chemistry 284, 23765-23779.|
|Appears in Collections:||(IQOG) Tesis|
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