The uridylytransferase-uridylyl removing enzyme (UT-UR) for glutamine synthetase regulatory cascade is known as the ultimate cellular nitrogen sensor in Escherichia coli. Its structural gene, glnD, was localized in between the genes of methionine aminopeptidase (map) and succinyl diaminopimelate aminotransferase (dapD) in the four minute region of the bacterial chromosome, through the maxicell technique and the detailed sequence analysis. The genetic order of the four minute genes is determined as follows: tsf-rpsB-map-glnD-dapD. The genes of map, glnD and dapD are transcribed in the direction opposite to rpsB-tsf. Since the glnD product, UT-UR, is known as the ultimate sensor for the nitrogen utilization system, its genetic relation with map attracted a new concern on the role of methionine aminopeptidase in the general nitrogen sensing system. Moreover, the S1 nuclease analysis and the primer extension study showed the possibility of the contranscription and the multiple initiation dependent on the source and level of nitrogen compounds for the growth medium.