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Toxicological Evaluation of SiO2 Nanoparticles by Zebrafish Embryo Toxicity Test

Increased susceptibility to oxidative stress-induced toxicological evaluation by genetically modified nrf2a-deficient zebrafish.

EGF receptor kinase suppresses ciliogenesis through activation of USP8 deubiquitinase

Chemokines protect vascular smooth muscle cells from cell death induced by cyclic mechanical stretch.

New photic stimulating system with white light-emitting diodes to elicit electroretinograms from zebrafish larvae.

tHydrophobic regions function in calmodulin-enzyme(s) interactions.


J Biol Chem. 1980 Dec 10;255(23):11078-80.

Hydrophobic regions function in calmodulin-enzyme(s) interactions.

Tanaka T, Hidaka H.


Certain naturally occurring lipids (phosphatidylinositol, phosphatidylserine, arachidonic acid) and sodium dodecyl sulfate activate at least two calmodulin-dependent enzymes, bovine brain 3':5'-cyclic nucleotide phosphodiesterase and chicken gizzard myosin light chain kinase in the absence of Ca2+. 2-p-Toluidinyl-naphthalene-6-sulfonate (TNS), which is often used as a probe for hydrophobic groups of proteins, inhibits these two calmodulin-dependent enzymes. Kinetic analysis of inhibition of chicken gizzard myosin kinase by TNS revealed a competitive fashion against calmodulin-induced activation. The interaction between TNS and purified bovine brain calmodulin as demonstrated in the appearance of TNS fluorescence in the presence of 3 microM or more of calcium ion was not observed in the presence of 2 mM EGTA. This suggests that TNS is able to bind to calmodulin in the presence of Ca2+. Moreover, a calmodulin-interacting agent N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide suppressed the TNS fluorescence induced by complex formation with calmodulin in the presence of Ca2+. These results suggest that when Ca2+ binds to the high affinity sites of calmodulin, it induces a conformational change which exposes hydrophobic groups, and the calmodulin is then capable of activating calmodulin-dependent enzymes. We propose that hydrophobic properties of Ca2+-calmodulin are important for the activation of Ca2+-calmodulin-dependent enzymes.

PMID: 6254958 [PubMed - indexed for MEDLINE]