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Research : Shyamalava Mazumdar

Bioinorganic Chemistry:  Redox Metalloenzymes and Biomimetic Chemistry

 We have been involved in the study of structural and mechanistic aspects of the biochemical function of electron transfer and redox metalloenzymes using various physicochemical techniques such as NMR (1 & 2D), Fluorescence (both equilibrium and time-resolved),  Circular dichroism (CD), Stopped -flow kinetics and Bioelectrochemistry of wild type, mutant proteins and their analogues with special interest on cytochrome c oxidase, cytochrome P450 and peroxidases. We are also involved in the study of interactions of surfactants and lipids with metal enzymes and their biochemical implications. Selected publications.

 

Cytochrome c Oxidase: The mechanism of transmembrane electron transfer and active proton pumping by the ubiquitous respiratory enzyme, cytochrome c oxidase (CcO) is a challenging area of research in bioinorganic chemistry. We have detected redox-state dependent conformational changes in this multi-metal enzyme and has shown that there is a localized conformational change in the enzyme due the electron transfer process.  Our studies showed that the conformational changes due to electron transfer and proton translocation are complementary to each other.  Our recent studies on pH induced conformational transition in genetically engineered dicopper site of cytochrome c oxidase demonstrated the possible role of this site in the gating mechanism of the electron transfer process of the enzyme. 
Cytochrome P450: Biosynthesis of steroid hormones, metabolism of drugs and many xenobiotics etc., are mediated by the metalloenzyme, cytochrome P450. The mechanism of drug metabolism, substrate recognition and product selectivity by this enzyme is a frontier area of research in bioinorganic chemistry. Studies of the interaction of physiologically important substrates with different cytochrome P450 enzymes by us helped to identify subtle conformational changes near the heme active site of the enzyme. 
We are also involved in extensive site-specific mutagenesis of the substrate access channel as well as the substrate binding site of this important enzyme with the aim of tuning the substrate specificity and product selectivity of the enzyme. 
Peroxidases: The conformational properties and stability of the metal active center are important for the biochemical function of metal enzymes and proteins. We have determined the specific contributions of hydrogen-bonding, ionic and hydrophobic interactions on the stabilization of the active site in the plant peroxidase and showed that the high stability of the enzyme against hydrogen peroxidase arises due to extensive hydrogen bonding and salt-bridges surrounding the metal center in the enzyme. Removal of the metal ion prosthetic group was shown to have a drastic effect on the structure of the enzyme and Our studied have also shown existence of multiple conformational sub-states in the apo-protein of the peroxidase in solution.
Interaction of Metal proteins with surfactants and lipids: Association of various surfactants and functional lipids with the membrane bound enzyme, cytochrome c oxidase and other heme proteins has very significant role in the biochemical function and stability of these biomolecules. We have shown that while ionic surfactants deactivate and cause depletion of the metal prosthetic group from most of the metal proteins, neutral surfactants help to stabilize the active structure in them. Our work has also suggested that the cardiotoxicity of the anti-cancer drug, adriamycin possibly arises due to seggregation of the functional lipid, cardiolipins associated with the cytochrome c oxidase leading to deactivation of the enzyme. We have shown that ionic surfactants can selectively unfold the metal active site of cytochrome c and stabilize an intermediate species, which is formed in the unfolding pathway of the enzyme. These studies have elucidated a fascinating chemistry of the action of surfactants and helped in better understanding of the varying degree of structural rigidity in the metal proteins. 

Selected Publications (click here for full list of publications):

Reversible inactivation of cytochrome P450 by alkaline earth metal ions: Auxiliary metal ion induced conformation change and formation of inactive P420 species in CYP101

Soumen K. Manna, Shyamalava Mazumdar

J. Inorg. Biochem. (2008) 5-6, 1312 - 1321

Effect of Polar Solvents on the Optical Properties of Water-dispersible Thiol-Capped Cobalt Nanoparticles

Nusrat J M Sanghamitra and Shyamalava Mazumdar

Langmuir (2008) 24 (7), 3439 - 3445

Conformational dynamics coupled to protonation equilibrium at the CuA site of T. thermophilus: Insights into the origin of thermostability

Nusrat J.M. Sanghamitra and Shyamalava Mazumdar

Biochemistry (2008) 47, 1309 - 1318

Thermostability of proteins: Role metal binding and pH on the stability of the dinuclear CuA site of Thermus thermophilus

A. Sujak, Nusrat J. M. Sanghamitra, O. Maneg, B. Ludwig and Shyamalava Mazumdar

Biophys. J. (2007) 93(8), 28452851

Effect of Alcohols on Binding of Camphor to Cytochrome P450cam: Spectroscopic and Stopped Flow Transient Kinetic Studies

R. Murugan and Shyamalava Mazumdar

Arch. Biochem. Biophys. (2006) 455(2), 154-162

Role of Threonine 101 on the stability of the heme active site of cytochrome P450cam: Multi-wavelength Circular Dichroism Studies

Soumen Kanti Manna and Shyamalava Mazumdar

Biochemistry (2006) 45(42), 12715 - 12722

Structure of the heme centre and its redox properties in the C357M mutant of cytochrome P450cam

R. Murugan and S. Mazumdar

ChemBioChem, (2005) 6, 1204-1211

Direct Correlation of the Crystal Structure of Proteins with the Maximum Positive and Negative Charge-States of Gaseous Protein Ions Produced by Electrospray Ionization

Halan Prakash and S. Mazumdar

J. Am. Soc. Mass Spectrom. (2005) 16, 1409-1421

Role of substrate on the conformational stability of the heme active site of cytochrome P450cam: effect of temperature and low concentrations of denaturants

R. Murugan and S. Mazumdar

J. Biol. Inorg. Chem. (2004) 9, 477-488

Stabilization of Partially Folded States of Cytochrome C in Aqueous Surfactant:

Effects of Ionic and Hydrophobic Interactions

K. Chattopadhyay and S. Mazumdar

Biochemistry (2003) 42, 14606 - 14613

pH induced conformational transition in the soluble CuA domain of Paracoccus denitrificans cytochrome oxidase

S. Gupta, A. Warne, Matti Saraste and S. Mazumdar

Biochemistry  (2001) 40, 6180-6189

Redox Linked Conformational Change in Bovine Heart Cytochrome c Oxidase: Picosecond Time-resolved Fluorescence Studies of the Cyanide Complex

T. K. Das and S. Mazumdar

Biopolymers: Biospectroscopy  (2000) 57,  316-322

Structural and Conformational Stability of Horseradish Peroxidase: Effect of Temperature and pH

K. Chattopadhyay and S. Mazumdar

Biochemistry, (2000) 39(1), 263-270.

Direct electrochemical oxidation of horseradish peroxidase: Cyclic Voltammetric and spectroelectrochemical studies

K. Chattopadhyay and S. Mazumdar

New J. Chem., (1999) 2, 137-139.


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