Uracil metabolism is an important step in the growth and metabolism of Streptococcus pneumoniae, and pyrimidine nucleotides play an important role in the expression and production of S. pneumoniae capsules. MgaSpn(spd_1587),as a transcriptional ragulator of host environment adaptation, regulates the biosynthesis of the capsules and phosphorylcholine. However, the underlying regulation mechanism between uracil metabolism and biosynthesis of capsules remains incompletely understood. Here, we first described the relationship between uracil metabolism and capsule expression via the pyrR gene(spd_1134) in S. pneumoniae. Electrophoretic mobility-shift assays (EMSAs) and DNase I footprinting assays showed a direct interaction between MgaSpn and the pyrR promoter (P