Chromium (III)-nucleotide complexes as paramagnetic probes for catalytic sites of phosphoryl transfer enzymes

Abstract

Cr/sup 3 +/-nucleotides, as exchange-inert, paramagnetic analogs of Mg/sup 2 +/-nucleotides, are useful paramagnetic probes for nuclear relaxation studies to determine intersubstrate distances between phosphoryl donor and acceptor substrates on phosphoryl transfer enzymes and, for enzymes with an additional metal ion site to estimate the intermetal distance between the enzyme- and nucleotide-bound metal ions. A basic assumption of this approach, that Cr/sup 3 +/-nucleotides bind at the Mg/sup 2 +/-nucleotide sites in a structurally similar manner, can be tested by observing kinetic inhibition patterns in the presence of Cr/sup 3 +/-nucleotides and, where possible, by their ability to activate partial reactions and to participate as substrates in phosphoryl transfer reactions.