Figure 5.

In vitro phosphorylation of N-terminal undeca-peptides of Drosophila synapsin at two substrate concentrations. The peptide encoded by the ''genomic'' sequence represents an excellent substrate for bovine PKA (compare with positive control ''Kemptide''). When a single amino acid of this peptide is modified by pre-mRNA editing (R4G) as encoded by the ''cDNA'', or when the two central serines are replaced by alanines (''mutated''), phosphorylation is abolished. Substrate concentrations (c) were 0.5 μg/μl and 1.0 μg/μl. Median, 25% – 75%, and Min-Max are shown. n indicates the number of independent measurements in each group. The difference in phosphate incorporation between genomic and cDNA peptides is significant at both substrate concentrations (p = 0.009).