Magnesium-binding site

FIGURE 8. Current model for the gating mechanism in the CorA transporter. Left closed conformation with the magnesium binding sites in the sensor occupied. Right postulated open conformation allowing ion transport into the ceU. Adapted by permission of MacmiUan Publishers Ltd. from Reference 71... 

Potter, J. D., and Gergely, J. (1975). The calcium and magnesium binding sites on troponin and their role in the regulation of myofibrillar adenosine triphosphatase. / Biol. Chem. 250, 4628-4633. 

Ryves WJ, Dajani R, Pearl L and Harwood AJ (2002) Glycogen synthase kinase-3 inhibition by lithium and beryllium suggests the presence of two magnesium binding sites. Biochem Biophys Res Commun 290 967 -972. 

Fig. 24. The magnesium-binding site in integrin [67]. Note that, two carboxylate groups, two hydroxy groups and one water molecule bind in such a manner that two ring motifs (each involving eight atoms) are formed. This coordination of magnesium ions serves to bind two portions of the molecule together...

Both enzymes have a single asparagine liganded to the catalytic magnesium ion and a catalytically important histidine nearby (His 89 in Serratia and His 98 in l-Ppot). However, in the absence of DNA, we find the magnesium binding site 3.8 A removed from this common binding site. 

In an X-ray analysis of the yeast tRNA , a specific magnesium-binding site in the vicinity of a G4-U69 wobble base pair was foimd. Thus it seemed attractive to study if a G-U pair is a specific binding site for magnesium ions. Addition of the diamagnetic Mg " cation has only little, though measurable, effects on the chemical shifts of the imino resonances (< 0.05 ppm). Since it is known from a number of biological and biochemical studies that... 

Fig. 8. Schematic model for three-dimensional structure of yeast tRNA" showing sugar-phosphate backbone, base pairs, five magnesium-binding sites (numbered circles), manganese site, ethidium-binding site, and spermine-binding site (dark curved shape in AC stem). Partially derived from Holbrook et al. (1978) and Kim (1979).

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