Albany 2015:Book of Abstracts
June 9-13 2015
©Adenine Press (2012)
Studies using molecular dynamics reveal mechanism of interaction of hemocyanin with phenolic substrates
Hemocyanin is a multimeric, type-3 copper containing, oxygen carrier protein that exhibits phenoloxidase-like activity and is found in select species of arthropoda and mollusca. The phenoloxidase activity in molluscan hemocyanin can be stimulated either by the proteolytic removal of its C-terminal β-rich sandwich domain (Campello et al. 2008) or by denaturation with SDS (Naresh, Krupanidhi & Rajan 2013), both of which enhance active site access to phenolic substrates (Coates & Nairn 2014). The mechanism of SDS-induced activation is however not well studied. We hypothesize that SDS mediated activation of phenoloxidase activity involves distortion of the secondary structure at the active site of the protein leading to enhanced substrate access. To address this, we used a combination of molecular dynamics simulations and docking on the crystal structure of a model molluscan hemocyanin from Octopus dofleini (PDB code:1JS8).
Our studies reveal SDS mediated displacement of the C-terminal β-domain along with the placeholder residue Leu2830 (see figure). These secondary structural distortions resulted in an enhanced substrate access to the protein's active site causing activation of phenoloxidase function.
This work was supported by BIF, Department of Biotechnology, Govt. of India, New Delhi.
Coates, C. J. & Nairn, J. (2014). Diverse immune functions of hemocyanins. Developmental & Comparative Immunology 45: 43-55.
Naresh, K. N., Krupanidhi, S. & Rajan, S. S. (2013). Purification, spectroscopic characterization and o-diphenoloxidase activity of hemocyanin from a freshwater gastropod: Pila globosa. Protein J 32: 327-336.
1 Department of Biosciences