Project	Genetics of immunity in silkmoths
Investigators PhD Scholars Technical Staff Research Associates	N Mrinal, Archana Gandhe
Collaborator	D Salunke, National Institute of Immunology, New Delhi
Funding Agency	Department of Biotechnology, Govt of India, New Delhi

Molecular analysis of lepidopteran specific immune proteins from silkmoths

The insect immune mechanism has aroused considerable interest in the recent years. Insects possess an innate immune system that shares some fundamental characteristics with the innate immune response of vertebrates. It is proposed that the study of immune response in simpler organisms like insects may give insight into the innate defense system of vertebrates. Insect immune system is characterized by an immediate early activation of prophenoloxidase cascade and a rapid induction of anti-microbial proteins and peptides upon microbial infection. We have undertaken a study on two antibacterial proteins in the silkworm namely gloverin like proteins and lysozyme like proteins.

Silkworm Lysozymes

Previous study in our lab has identified a lysozyme like protein in domesticated silkworm, Bombyx mori and Indian tasar silkworm, Antheraea mylitta. Also the crystal structure of A. mylitta lysozyme is demonstrated in our lab which is the first insect lysozyme structure reported. These silkworm c-type lysozymes are interesting in terms of their unique properties with respect to chicken lysozymes (HEWL). Also certain differences with respect to activity have been found between the B. mori and A. mylitta lysozymes. The major objective set out in the project is to determine the molecular mechanisms of lysozyme action based on the structure-function analysis of the proteins from A.mylitta and B.mori and also to determine the biological role of lysozyme.

1.Characterisation and functional studies

We have isolated and determined the sequence of A.mylitta lysozyme (AL). Both AL and B.mori lysozyme (BL) are being expressed in a recombinant expression system. We are currently characterizing the enzymes in terms of their activity, anti-bacterial spectrum and also studying their importance in silkworm immunity.

2. Structural comparison of AL, BL and HEWL: Protein engineering

The structural comparison shows distinct differences between the AL and BL and also HEWL. We intend to utilize these differences in the structure as a guideline in designing the mutants to understand the molecular mechanisms of lysozymes. Also we plan to use in-silico protein homology modeling to further narrow down the residues to be mutated.

3. Future work: Structure -function correlation of the insect lysozymes

Based on this study we plan to make lysozyme mutants, determine its activity and compare it with that of wild type proteins. This will throw light upon the structure -function relationship of the lysozymes.