Abstract:Ketoreductase (KR) is an important component of polyketide synthase (PKS) that can catalyze the reduction of β-keto groups and is employed in synthesizing chiral drugs. In addition, it plays a key role in the synthesis of polyketide compounds. A 1,331 bp KR domain gene was amplified from Streptomyces sp. X-66 genomic DNA and subjected to bioinformatics analysis herein. BLAST alignment results showed that the sequence consisted of FAS KR and PKS KR, and its core functional region was concentrated in a region of the PKS KR gene sequence. The maximum ORF region was estimated to encode 333 amino acids, with a theoretical isoelectric point of 4.80, and a molecular formula of C1500H2419N433O463S6. The instability index was 24.85. It is speculated that the coding product is an acidic stable protein with low hydrophilicity, without signal peptides or transmembrane structures. The secondary structure was primarily comprised of α-helices and random coils. SDS-PAGE results suggested that its relative molecular weight was ~70 ku. Amino acid multiple sequence alignment revealed that the KR3 protein belongs to the B1-type KR. Subsequently, the amino acid sequence of KR3 was used to predict and test its tertiary structure model. According to molecular docking and visualization analysis, the key residues involved in the binding of KR3 protein to its ligand were predicted to be 204Thr, 206Thr, and 207Leu. According to relevant studies, the binding mode in which KR3 protein guides the substrates into the active center is consistent with B-type KR. These findings provide a scientific basis for further investigation into the functions of KR3 and the synthesis of new chiral drugs and polyketides.
