High-resolution proton nuclear magnetic resonance studies of the glucocerebrosidase activator protein from Gaucher spleen.

ABSTRACT

A heat-stable protein factor (HSF) obtained from the spleen of a patient with Gaucher's disease that activates glucocerebrosidase was studied by 600-MHz proton NMR spectroscopy. Assignments for a number of aromatic and aliphatic resonances were made on the basis of spin-decoupling, pH-titration, and resolution-enhancement experiments. The upfield ring current shifted aliphatic region and the downfield aromatic region were examined by nuclear Overhauser effect (NOE) methods using both pulsed Fourier-transform spectroscopy and correlation spectroscopy. It was found that a number of upfield-shifted methyl groups and certain methylene groups of specific aliphatic amino acid residues are in proximity relationships with several aromatic residues, forming a compact hydrophobic clustering site. Of special interest, tyrosine A, phenylalanine A, tryptophan B1, and tryptophan B2 were found to be located close to a cluster of aliphatic residues, indicating that the hydrophobic site of the HSF is conformationally rigid and its tertiary structure very compact. A two-dimensional structural model of the hydrophobic site of HSF is proposed.