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Figure 3.
FIG. 3. Substitutions of residues participating in the
hydrogen-bonding network result in markedly decreased reductive
acylation (Reaction 3) activity. Invariant residues (Arg287-
 ,
Asp295- , Tyr300- , and
Arg301- ) that form the
hydrogen-bonding network were changed to alanine or
phenylalanine in the case of Tyr300- . Reductive acylation
of lip-LBD catalyzed by wild-type or mutant E1b was measured
with [U-14C]KIV as a substrate as described under "Experimental
Procedures." Activity for reductive acylation is expressed as
percent relative to the wild type (2.3 min-1). The nonspecific
radioactivity incorporated into nonlipoylated LBD and the
wild-type or mutant E1b protein served as a blank. Results are
averages of two independent experiments.
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