Cell and Molecular Biology Laboratory, Interactive Research School for Health Affairs, Bharati Vidyapeeth University, Pune-Satara Road, Pune 411043, India.
J Sci Food Agric. 2011 Nov;91(14):2689-96. doi: 10.1002/jsfa.4515. Epub 2011 Jul 18.
Desaturases are enzymes that drive the multi-step fatty acid biosynthetic pathway. As evident from directed mutagenesis, single base changes in their polypeptide can potentially alter their structure and may result in altered substrate specificity, regioselectivity and even loss of function. The authors have previously isolated several sequence variants of Δ15 desaturase from flax while attempting to clone that gene. The aim of the present study was to analyse these gene variants for their functionality and to predict the tertiary structure of the protein in order to correlate the functional differences with the protein structure.
The variants differed in the rate at which they could convert linoleic acid to α-linolenic acid. The highest conversion rate was 7.03%, while the lowest was 2.39%. The overall shape of the predicted 3D model of the protein is a compact cylinder containing α-helices and β-sheets. The Ramchandran plot of this model revealed that 98.5% of the residues are located in allowed region, which denotes a stable structure.
Although the structures of the variants are apparently similar, subtle changes account for variation in their activity. Besides, these substitutions may alter their cross-talk with other proteins and thus differentially influence their specificity, localisation and stability, which in turn may explain the diversity in their function.
去饱和酶是驱动多步脂肪酸生物合成途径的酶。从定向诱变明显看出，其多肽中的单个碱基变化可能改变其结构，并可能导致改变的底物特异性、区域选择性甚至丧失功能。作者在试图克隆该基因时，以前从亚麻中分离出几种 Δ15 去饱和酶的序列变体。本研究的目的是分析这些基因变体的功能，并预测蛋白质的三级结构，以便将功能差异与蛋白质结构相关联。
变体在将亚油酸转化为α-亚麻酸的速度上有所不同。最高转化率为 7.03%，而最低转化率为 2.39%。该蛋白质的预测三维模型的整体形状是一个包含α-螺旋和β-折叠的紧凑圆柱体。该模型的 Ramchandran 图显示，98.5%的残基位于允许区域，这表示结构稳定。
尽管变体的结构显然相似，但细微的变化导致了它们活性的变化。此外，这些取代可能改变它们与其他蛋白质的相互作用，从而不同地影响它们的特异性、定位和稳定性，这反过来又可以解释它们功能的多样性。
