Chaperonins mediate protein folding in an ATP-dependent manner. ATP binding and hydrolysis by chaperonins are subject to both homotropic and heterotropic allosteric regulation. In the case of GroEL and CCT, homotropic regulation by ATP is manifested in nested cooperativity, which involves positive intra-ring cooperativity and negative inter-ring cooperativity in ATP binding. Both types of coope...

Haptoglobin (Hp) is a mammalian serum glycoprotein showing a genetic polymorphism with three types, 1-1, 2-2 and 1-2. Hp appears to conserve the recycling of heme-iron by forming an essentially irreversible but non-covalent complex with hemoglobin which is released into the plasma by erythrocyte lysis. As an important consequence, Haptoglobin-Hemoglobin complex (Hp-Hb) shows considerable antiox...

Protein allostery is essential for vital activities. Allosteric regulation of human hemoglobin (HbA) with two quaternary states T and R has been a paradigm of allosteric structural regulation of proteins. It is widely accepted that oxygen molecules (O2) act as a "site-specific" homotropic effector, or the successive O2 binding to the heme brings about the quaternary regulation. However, here we...

Muscarinic agonists and adenyl nucleotides are noncompetitive modulators of sites labeled by [35S]GTP gamma S in washed cardiac membranes from Syrian golden hamsters. Specific binding of the radioligand and its inhibition by either GTP gamma S or GDP reveals three states of affinity for guanyl nucleotides. In the absence of adenyl nucleotide, carbachol promotes an apparent interconversion of si...

We review results on theoretical modeling of biochemical systems in support of the studies of several types of biosensors and systems for “biocomputing” information processing. The developed theoretical techniques have been utilized to investigate performance and optimize a novel approach to biosensors with extended linear response for lysine detection and also to study a “binary” response of a...

Carbon monoxide binding by myoglobin and hemoglobin has been studied under conditions of constant illumination. For hemoglobin, the homotropic heme-heme interaction (cooperativity) and the heterotropic Bohr effect are invariant with light intensity over a 1000-fold change of c((1/2)). The dissociation constant, measured as c((1/2)), increases linearly with light intensity, indicating that photo...

This paper is focused on the study of skeleton transformations involved in the hand printed & handwritten documents’ images preprocessing. A new homotropic transformation structural element is proposed in order to optimize the sequential thinning procedure: reduced number of thinning cycles and less coarse skeleton lines. Key-Words: Hand-written Character Recognition, homomorfic transformation,...

Stabilization of the T and R allosteric states of Escherichia coli aspartate transcarbamoylase is governed by specific intra- and interchain interactions. The six interchain interactions between Glu-239 in one catalytic chain of one catalytic trimer with both Lys-164 and Tyr-165 of a different catalytic chain in the other catalytic trimer have been shown to be involved in the stabilization of t...

Cytochrome P450's (P450's) catalyze the oxidative metabolism of most drugs and toxins. Although extensive studies have proven that some P450's demonstrate both homotropic and heterotropic cooperativity toward a number of substrates, the mechanistic and molecular details of P450 allostery are still not well-established. Here, we use UV/vis and heteronuclear nuclear magnetic resonance (NMR) spect...