Characterization of Lovastatin biosynthetic cluster proteins in Aspergillus terreus strain ATCC 20542.

Thankaswamy Kosalai Subazini,Gopal Ramesh Kumar

doi:10.6026/97320630006250

Abstract

Aspergillus terreus is a filamentous ascomycota, which is prominent for its production of lovastatin, an antihypercholesterolemic drug. The commercial importance of lovastatin with annual sales of billions of dollars made us to focus on lovastatin biosynthetic cluster proteins. The analysis of these lovastatin biosynthetic cluster proteins with different perspectives such as physicochemical property, structure based analysis and functional studies were done to find out the role and function of every protein involved in the lovastatin biosynthesis pathway. Several computational tools are used to predict the physicochemical properties, secondary structural features, topology, patterns, domains and cellular location. There are 8 unidentified proteins in lovastatin biosynthetic cluster, in which 6 proteins have homologous partners, and annotation transfer is done based on the closely related homologous genes, and their structures are also modeled. The two other proteins that do not have homologous partners are predicted as PQ loop repeat protein that may be involved in glycosylation machinery and as thiolase-acyl activity by the integrated functional analysis approach.

Highlights

Aspergillus terreus, an important fungus is a major source for lovastatin, which treats cardiovascular disease by effectively inhibiting HMG CoA reductase activity, the rate limiting step in cholesterol biosynthesis
Out of the 18 lovastatin biosynthetic cluster proteins it is found that 2 proteins are involved in regulatory mechanisms, 3 in transportation, 9 enzymes, 2 unknown proteins of thiolases acyl-enzyme intermediate signature and PQ loop repeat, and 2 megasynthases, [2] Lovastatin Nonaketide Synthase (LNKS) and Lovastatin Diketide Synthase (LDKS)
Primary sequence analysis: The primary sequence analysis revealed that the grand average of hydropathicity (GRAVY) indices of 13 lovastatin biosynthetic proteins are ranging from – 0.03 to -0.5, which indicates they are hydrophilic and mostly predicted to be localized in extracellular and mitochondrial regions, the other 5 proteins (PQ loop repeat containing protein, HMG-CoA reductase, the 2 Permeases of the major facilitator superfamily, tricarboxylate transport protein) are hydrophobic (GRAVY values range from 0.05 to 0.6) and are localized in plasma membrane and basic in nature with pH value greater than 7

Summary

Introduction

Aspergillus terreus, an important fungus is a major source for lovastatin, which treats cardiovascular disease by effectively inhibiting HMG CoA reductase activity, the rate limiting step in cholesterol biosynthesis. The insilico analysis of physicochemical properties along with their topology and the functional analyses of these proteins are done by integrating standard functional annotation tools available online based on different methodologies. The final verification of functions of unknown proteins is done by structure based analysis.

Results

Conclusion