title: Is atomic rearrangement of type IV PHA synthases responsible for increased PHA production?
abstract: BACKGROUND
  Type IV PHA synthase is a key enzyme responsible for catalyzing the formation of non-toxic, biocompatible, and biodegradable short-chain-length polyhydroxyalkanoates (scl-PHA) under the growth-limiting conditions in the members of the genus Bacillus.
  
  
  RESULTS
  The comparative in vitro and in silico analysis of the phaC subunit of type IV PHA synthases among Bacillus cereus FA11, B. cereus FC11, and B. cereus FS1 was done in our study to determine its structural and functional properties. Conserved domain analysis demonstrated that phaC subunit belongs to the alpha/beta (α/β) hydrolase fold. The catalytic triad comprising of cysteine (Cys), histidine (His), and aspartate (Asp) was found to be present at the active site. A shorter inter-atomic distance was found between the carboxyl (-COO) group of Asp and amino (NH2) group of His. Furthermore, slightly long inter-atomic distances between sulfhydryl (SH) group of Cys and NH2 group of His may be pointing toward the broader substrate specificity of type IV PHA synthases. However, a shorter distance between the SH group of Cys and NH2 group of His in case of B. cereus FC11 leads to a higher enzymatic activity and maximum PHA yield (49.26%).
  
  
  CONCLUSIONS
  The in silico study verifies that the close proximity between SH group of Cys and NH2 group of His in phaC subunit of type IV PHA synthases can be crucial for synthesis of scl-PHA. However, the catalytic activity of type IV PHA synthases declines as the distance between the sulfur (S) atom of the SH group of Cys and the nitrogen (N) atom of NH2 group of His increases.
authors: a Department of Biosciences , COMSATS Institute of Information Technology (CIIT) , Islamabad , Pakistan.
authors: Aamira
authors: A
authors: Tariq
authors: Abdul
authors: A
authors: Hameed
authors: Habib
authors: H
authors: Bokhari
authors: Farha
authors: F
authors: Masood
mesh_terms: D000217:Acyltransferases / Q000737:chemistry* / Q000145:classification / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D004926:Escherichia coli / Q000378:metabolism; D005285:Fermentation; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D054813:Polyhydroxyalkanoates / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D021122:Protein Subunits; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D054813:Polyhydroxyalkanoates; D021122:Protein Subunits; D000217:Acyltransferases; C077225:poly(3-hydroxyalkanoic acid) synthase
keywords: biodegradable; lipase box; phaC subunit; polyhydroxyalkanoates; threading; α/β hydrolase fold