Streptomyces metal-binding sites

Arginine is capable of binding in the active site of PAH but it is not an enzyme substrate. Crystal structures of PAH from Streptomyces clavuligerus show that the metal binding site is very similar to that of arginase and the Mn—Mn distance is 3.3 A The main difference between arginase and PAH is in the binding pocket at the o-amino-terminus of the substrate. ... 

The information that there is a high probability that the metal lies in the carboxyl plane, but with possible deviations for specific metals, provides a mechanism for searching for metal-binding positions in proteins. This method was used in a study of the enzyme xylose isomerase from Streptomyces rubiginosus (Carrell et al., 1989). Two metal sites were located. One metal-binding site involves three carboxylates (aspartate and glutamate), histidine, and water, and the other involves four carboxylate... 

One of the characteristics of protein calcium channels is their sensitivity to ablock by transition metal cations. Lanthanum is a particularly potent blocker. It is suggested that permeant and blocking ions compete for the common binding sites in the channels. The PolyP-PHB channel complexes are also blocked by transition metal cations in a concentration-dependent manner. A nearly complete block of single-channel currents was observed in the synthetic complexes at concentations > 0.1 mM La3+ (0.1 % of Ca2+) (Das et al., 1997). Evidently, PHB-PolyP complexes are versatile ion carriers whose selectivities may be modulated by small adjustments of the local pH. The results may be relevant to the physiological function of PHB-PolyP channels in bacteria and the role of PHBs and PolyPs in the Streptomyces lividans potassium channel (Das and Reusch, 2001). 

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