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Efecto de la alanina frente a la glicina en las hélices alfa sobre la estabilidad de las proteínas
L Serrano1, J L Neira, J Sancho
1MRC Unit for Protein Function and Design, MRC Centre, Hills Road, Cambridge CB2 2QH, UK.
Nature
|April 2, 1992
Resumen
La estabilidad de la hélice proteica depende de la posición de los aminoácidos. La alanina estabiliza las posiciones internas de la hélice, mientras que la glicina se prefiere en los extremos de la hélice, desafiando los valores universales de propensión a formar hélices.
Área de la Ciencia:
- La bioquímica de las proteínas.
- Biología estructural Biología estructural.
- La biofísica es la biofísica.
Sus antecedentes:
- El diseño racional de proteínas se basa en la comprensión de las propensiones de formación de hélices de aminoácidos (valores-s).
- Existe un debate significativo con respecto a las propensiones relativas a la formación de hélices de la alanina (Ala) y la glicina (Gly).
Objetivo del estudio:
- Investigar los efectos dependientes del contexto de la alanina y la glicina en la estabilidad de la hélice de la proteína.
- Para determinar si un valor s universal para cada aminoácido es aplicable en todas las posiciones helicoidales.
Principales métodos:
- Análisis experimental de los mutantes de la barnasa.
- Evaluación de la estabilidad de la hélice basada en las sustituciones de aminoácidos en diferentes posiciones helicoidales (caps vs. internal).
Principales resultados:
- El impacto relativo de Ala versus Gly en la estabilidad de la hélice es dependiente de la posición.
- La glicina es fuertemente favorecida en las tapas de la hélice de los terminales N y C.
- La alanina estabiliza las posiciones de la hélice interna en relación con la glicina en 0.42 kcal mol-1.1.
- Las variaciones observadas se correlacionan con cambios en la superficie hidrofóbica accesible al disolvente y en el enlace hidrógeno disolvente-proteína.
Conclusiones:
- Un único valor s universalmente aplicable para cada aminoácido no es válido.
- Las propensiones a formar hélices están influenciadas por el contexto de la secuencia local y la posición dentro de la hélice.
- Estos hallazgos refinan nuestra comprensión del plegamiento de proteínas y la estabilidad para el diseño racional de proteínas.
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