ATP and GTP Competition Assays for Serp1129. (A) ATP and GTP binding assay. The lane marked "0" indicates that no unlabeled ATP or GTP was added to the reaction and increasing levels (5, 10, 20, and 30 μM) of unlabeled ATP or GTP are indicated by the triangle above the appropriate lanes. The lanes marked as "-" are the negative control containing CidA , which does not bind ATP or GTP. B. SDS-PAGE loaded with the same protein concentration of Serp1129 as in Figure 6A and stained with Coomassie Blue; shown as a loading control.