1AJB

THREE-DIMENSIONAL STRUCTURE OF THE D153G MUTANT OF E. COLI ALKALINE PHOSPHATASE: A MUTANT WITH WEAKER MAGNESIUM BINDING AND INCREASED CATALYTIC ACTIVITY

Summary for 1AJB

• Entry DOI: 10.2210/pdb1ajb/pdb
• Descriptor: ALKALINE PHOSPHATASE, ZINC ION, MAGNESIUM ION, ... (5 entities in total)
• Functional Keywords: non specific mono-esterase
• Biological source: Escherichia coli
• Cellular location: Periplasm: P00634
• Total number of polymer chains: 2
• Total formula weight: 94577.07

Authors

Dealwis, C.G.,Chen, L.,Abad-Zapatero, C. (deposition date: 1995-08-19, release date: 1995-11-14, Last modification date: 2024-10-23)

Primary citation

Dealwis, C.G.,Chen, L.,Brennan, C.,Mandecki, W.,Abad-Zapatero, C.
3-D structure of the D153G mutant of Escherichia coli alkaline phosphatase: an enzyme with weaker magnesium binding and increased catalytic activity.
Protein Eng., 8:865-871, 1995

PubMed Abstract: The substitution of aspartate at position 153 in Escherichia coli alkaline phosphatase by glycine results in a mutant enzyme with 5-fold higher catalytic activity (kcat) but no change in Km at pH 8.0 in 50 mM Tris-HCl. The increased kcat is achieved by a faster release of the phosphate product as a result of the lower phosphate affinity. The mutation also affects Mg2+ binding, resulting in an enzyme with lower metal affinity. The 3-D X-ray structure of the D153G mutant has been refined at 2.5 A to a crystallographic R-factor of 16.2%. An analysis of this structure has revealed that the decreased phosphate affinity is caused by an apparent increase in flexibility of the guanidinium side chain of Arg166 involved in phosphate binding. The mutation of Asp153 to Gly also affects the position of the water ligands of Mg2+, and the loop Gln152-Thr155 is shifted by 0.3 A away from the active site. The weaker Mg2+ binding of the mutant compared with the wild type is caused by an altered coordination sphere in the proximity of the Mg2+ ion, and also by the loss of an electrostatic interaction (Mg2+.COO-Asp153) in the mutant. Its ligands W454 and W455 and hydroxyl of Thr155, involved in the octahedral coordination of the Mg2+ ion, are further apart in the mutant compared with the wild type.

PubMed: 8746724
DOI: 10.1093/protein/8.9.865

Experimental method

X-RAY DIFFRACTION (2.5 Å)