Table I. GUS activity of mutant GUS proteins synthesized in vitro
Codon 11 Amino AcidaCodon SequenceSpecific ActivitybCodon 11 Amino AcidcCodon SequenceSpecific Activityb
%%
Glu (wild type)GAA(100.0)HisCAT0.1
StopTAA0.7IleATA1.4
GlyGGA8.7LeuCTA1.0
GlnCAA27.0AsnAAT1.5
AlaGCA7.9ProCCA0.4
ValGTA0.8ArgAGA0.2
LysAAA1.1SerTCA1.2
AspGAT45.4ThrACA0.5
Frame shiftedd(A)80.9TyrTAT0.04
  • a Proteins designated according to the amino acid at codon 11 of the E. coli uidA (GUS) gene, as specified by the indicated “reporter” codons.

  • b Indicated (35S-labeled) proteins encoded by reporter lines MR1 to MR6 (Fig. 1) were synthesized by in vitro transcription and translation. GUS activities were measured as cleavage of fluorogenic (MUG) substrate, as described in “Materials and Methods,” and normalized for protein concentrations determined by SDS-PAGE and quantitative autoradiography.

  • c Proteins designated according to amino acids that would be encoded by the indicated mutant codons.

  • d Frame-shift mutation (TA) constructed immediately downstream of codon 11 (5′-GAAATAAAAAAAA-3′) would generate a stop codon 60 bases farther downstream.