Cellular ligands

M. Gerloch, The Cellular Ligand-Field Model , in Understanding Molecular Properties, (Eds. J.S. Avery, J.P. Dahl, A.E. Hansen), Reidel, 1987, p.lll. 

Despite the title in reference (6), both references (6) and (7) describe the cellular ligand-field model. 

The CLF/MM method, described in Chapter 2, Section 2.2.2, uses a cellular ligand field stabilization term and arrives at relatively accurate predictions of Jahn-Teller distortions. 

In this approach the metal-ligand interaction is modeled with a metal-ligand bonding interaction term, ML, approximated by a Morse function, a cellular ligand field stabilization energy term, (which is responsible for the coordination... 

Han, L, Yoshihara, ., Mizono, T-, Mori, K., and Gahmberg, C G. (1997). The neuronal glycoprotein telencephalin is a cellular ligand for CDlla/CDlS leukocyte integnn. /. Itatmmai 158,928-936. 

The central importance of free metal-ion activities in controlling the biological effects does not necessarily mean that the free aquo metal ions are actually the chemical species taken up by aquatic organisms. It reflects the fact that the chemical reactivity of a metal is measured by the free metal-ion activity and that the physiological effects of a metal are mediated by chemical reactions between the metal and the various cellular ligands (Morel and Hering, 1993). 

Thus, the toxicity of DMM is mediated by its dealkylation. Cleavage of the carbon-mercury bond generates MMM metabolites, which can form covalent bonds with cellular ligands with amphiphilic properties. The mercury center reacts with sulfur and sulfur-containing thiol groups of enzymes and thereby inhibits them. The metal center of DMM acts as a soft acid, and binds tightly to polarizable donor atoms in soft bases. Within cells, mercury may interact with a variety of proteins, particularly microsomal and mitochondrial enzymes. This can severely impair cell function. 

The receptor-like protein tyrosine phosphatases have a transmembrane and, in some cases, a large extracellular domain with a very variable structure (Fig. 8.19). Many, but not all, membrane protein tyrosine phosphatases have two catalytic domains in the cytoplasmic region. The overall structure is very similar to the structure of transmembrane receptors. Only recently, cellular ligands for receptor tyrosine phosphatases have been identified that function as their specific regulators. The receptor tyrosine phosphatase C has been found to be specifically inhibited by pleiotrophin, which is a cytokine implicated in tumor angiogenesis. Several studies have demonstrated a role for receptor PTPs in neuronal cell adhesion signaling pathways. In cells of the neural tissue, a surface protein, contactin, has been identified as an extracellular ligand of PTPa. 

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