title: Functional and bioinformatic characterisation of sequence variants of Fad3 gene from flax.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Cell and Molecular Biology Laboratory, Interactive Research School for Health Affairs, Bharati Vidyapeeth University, Pune-Satara Road, Pune 411043, India.
authors.forename: Rupali
authors.initials: R
authors.lastname: Khadake
authors.forename: Vijaykumar
authors.initials: V
authors.lastname: Khonde
authors.forename: Vaishali
authors.initials: V
authors.lastname: Mhaske
authors.forename: Prabhakar
authors.initials: P
authors.lastname: Ranjekar
authors.forename: Abhay
authors.initials: A
authors.lastname: Harsulkar
mesh_terms: D000595:Amino Acid Sequence; D016718:Arachidonic Acid / Q000378:metabolism; D001665:Binding Sites; D019295:Computational Biology / Q000379:methods*; D030562:Databases, Protein; D044943:Fatty Acid Desaturases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D019597:Flax / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D014644:Genetic Variation; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D019787:Linoleic Acid / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012639:Seeds / Q000201:enzymology / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D007527:Isoenzymes; D050505:Mutant Proteins; D011994:Recombinant Proteins; D016718:Arachidonic Acid; D019787:Linoleic Acid; D044943:Fatty Acid Desaturases; C094563:delta-15 desaturase