The mechanisms of acute copper and silver toxicity in freshwater organisms appear similar. Both result in inhibition of branchial sodium (and chloride) uptake initiating a cascade of effects leading to mortality. The inhibition of the branchial Na/K-ATPase in the basolateral membrane is generally accepted as the key component responsible for the reduced sodium uptake. We propose that branchial ...

Protein molecular adaptation to drastically shifting salinities was studied in dCA II, an alpha-type carbonic anhydrase (EC 4.2.1.1) from the exceptionally salt-tolerant unicellular green alga Dunaliella salina. The salt-inducible, extracellular dCA II is highly salt-tolerant and thus differs from its mesophilic homologs. The crystal structure of dCA II, determined at 1.86-A resolution, is glob...

Carbonic anhydrases (CAs) are ubiquitous Zn metallo-enzymes that catalyze the reversible hydration/dehydration of CO2/HCO3(-). CAs are involved in many key biological processes, therefore their inhibition has become an attractive research field. Distinct families of CA inhibitors (CAIs) have been reported, most of them interacting with the Zn(II) at the active site. Some compounds such as the c...

This paper uses crystals of bovine carbonic anhydrase (CA) and its acetylated variant to examine (i) how a large negative formal charge can be accommodated in protein-protein interfaces, (ii) why lysine residues are often excluded from them, and (iii) how changes in the surface charge of a protein can alter the structure and organization of protein-protein interfaces. It demonstrates that acety...

Soluble adenylyl cyclase (sAC) is a source of the second messenger cyclic adenosine 3', 5' monophosphate (cAMP). sAC is directly regulated by bicarbonate (HCO(-) 3) ions. In living cells, HCO(-) 3 ions are in nearly instantaneous equilibrium with carbon dioxide (CO2) and pH due to the ubiquitous presence of carbonic anhydrases. Numerous biological processes are regulated by CO2, HCO(-) 3, and/o...

Carbonated beverages are commonly available and immensely popular, but little is known about the cellular and molecular mechanisms underlying the perception of carbonation in the mouth. In mammals, carbonation elicits both somatosensory and chemosensory responses, including activation of taste neurons. We have identified the cellular and molecular substrates for the taste of carbonation. By tar...

Water oxidation in photosystem II (PSII) is still insufficiently understood and is assumed to involve HCO(3)(-). A Chlamydomonas mutant lacking a carbonic anhydrase associated with the PSII donor side shows impaired O(2) evolution in the absence of HCO(3)(-). The O(2) evolution for saturating, continuous illumination (R(O2)) was slower than in the wild type, but was elevated by HCO(3)(-) and in...

Carbonic anhydrase (CA) III is very abundant in type I skeletal muscle, but its function is still debated. Our aims were to examine CA III expression during growth and determine whether the effects of CA inhibition previously observed in adult muscles could be seen in younger rats in which CA III levels are lower. CA III content and activity were measured in soleus muscles from 10- to 100-day-o...

The ability to construct molecular motifs with predictable properties in aqueous solution requires an extensive knowledge of the relationships between structure and energetics. The design of metal binding motifs is currently an area of intense interest in the bioorganic community. To date synthetic motifs designed to bind metal ions lack the remarkable affinities observed in biological systems....

The kinetic parameters for carbon dioxide hydration catalysis by carbonic anhydrase (EC 4.2.1.1) present an apparent paradox. The assumption of H(2)CO(3) as the hydration product requires the rate of recombination of H(2)CO(3) with enzyme to be faster than the diffusion limit. The alternative assumption of HCO(3) (-) as the product of hydration likewise requires active-site ionization rates to ...