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Abstract

Objective:The cockroach milk protein (CMP) is found in the mid-gut of a Pacific Beetle Viviparous cockroach in liquid state. This becomes crystals due to the ingestion by embryos in the midgut.The main aim of this study is to identify distant homologs of the CMP from sequence and structure perspective. Methods:In this study we carried Fold based approaches like pDomTHREADER and pGenTHREADER to identify distant homologs. Multiple sequence alignment (MSA) was performed to identify sequence identity between homologous proteins. PRINTS, PRODOM and PROSITE were used for protein domain analysis.Structural superimposition of CMP with Bacterial Outer Membrane Lipoprotein (Blc) of E. coli and Apolipoprotein D (ApoD) of Homo sapiens were carried out using Chimera. Finally, the domain mobility was studied using iMODs online server. Results: Based on the fold based method, CMP is closely related to Blcprotein (E.Coli). From alignment perspective, CMP and ApoD exhibits higher sequence similarity compared to Blc and Lazarillo (Schistocerca americana). Furthermore, protein domain of ApoD was identified to be of lipocalin family as per the PROSITE database search. From structural perspective, both CMP and ApoD superimposes well with each other. Furthermore, CMP shows lesser domain mobility compared to Blc and ApoD protein due to the presence of proline residues. This data reveals significant evolution of proteins during speciation. Conclusion: Significant structural similarities were observed between CMP and ApoD. The sequential and structural aspects of cockroach milk protein holds further scope for comparative analysis between lipocalin families based on different adaptation or protein modifications.