J. Biol. Chem., Vol. 260, Issue 28, 15055-15058, 12, 1985
Probing the renin active site by collisional quenching of endogenous fluorescence
SC Quay, A Heropoulos, K Commes and VJ Dzau
The structural and enzymatic aspects of renin are of great interest in
hypertension research. In this paper, we examine the solution accessibility
of the three tryptophan (Trp) residues of mouse submaxillary gland renin by
solute collisional fluorescence quenching. Our studies indicate that there
are two "classes" of Trp residues in renin: class I, a class of Trp
residues which are at or near the surface of renin and fully accessible to
the fluorescence quencher iodide; and class II, a class of Trp residues
which are, for practical experimental conditions, totally inaccessible to
the aqueous solution. The former class contains 2 Trp residues, while only
a single Trp is identified in the latter class. The presence of a
tetradecapeptide substrate or a nonhydrolyzable substrate analogue (peptide
H-77) lowers the accessibility of iodide to the class I Trp residues. These
data indicate that the class I Trp residues are at or near the peptide-
binding site of renin. In addition, the finding that the class I Trp
residues are quantitatively quenched more efficiently than the Trp model
compound indole suggests that the environment of the class I tryptophans
may be positively charged, and thus have a higher "local" concentration of
iodide. These data, taken together with the available sequence and
computer-generated three-dimensional structure of renin, permit us to
speculate that the class I Trp residues are Trp-39 and Trp- 300. This
solution study of renin structure is discussed in light of the known
information about renin catalysis and physiology.
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