Figure 2.

Nucleotide sequence of nifH promoter region and mutations. The promoter and translational start sites are underlined, palindromic sequences overlined, and transcriptional start site indicated by  Γ. Mutations are indicated in parentheses. Mutations altering the first, second, and both halves of the first palindrome are designated CT1, AG1, and CT1AG1, respectively. Similar mutations in the second palindrome are CT2, AG2, and CT2AG2. A mutation making the first palindrome identical to the second is TA3T, and a mutation deleting six nucleotides between the two palindromes is Δ6.