Acid phosphatase model studies

Earlier, we have reviewed the most fundamental properties about zincdD s nucleophilicity and the basicity of L— Zn —OH (L = model ligands such as macrocyclic polyamines or tris(pyrazolyl)borate) (6). More recent model studies by us and other groups have been trying to answer further questions (i) Why (or how) is serine needed in alkaline phosphatase More indirectly, what are the points of the serine OH group intervening as acyl- or phosphoryl-transfer agents (ii) Why is a bimetallic system favorable for phosphate hydrolysis (iii) Why does nature adopt zinc(II) as a Lewis acid in zinc enzymes or imidazole as a Lewis base (in the serine-imidazole-carboxylate triad) in serine enzymes (iv) Why are four zinc(II)-bound cysteines used for demethyl-ation (repair) of methyl-DNA phosphotriester, damaged DNA In this review, we want to present the latest results related to these puzzles. 

Recently, the E. coli SecB was coexpressed in a subtilis strain with a modified SecA protein. Specifically, the 32 C-terminal residues of SecA of B. subtilis were replaced by the corresponding amino acids of E. coli SecA to optimize the SecA-SecB interaction. This engineering of the protein secretion machinery resulted in the increased secretion of a mutant maltose-binding protein (MalEl 1) and the alkaline phosphatase PhoA of . coli, which were used as model heterologous proteins [63]. It should be noted here that early studies by Collier also provided evidence that the heterologous expression of E. coli SecB in B. subtilis could be beneficial for the secretion of particular proteins [64]. 

---