The lactose (lac) operon of E. coli

(a) The repressor protein (lacI) is encoded by a 1040-bp segment under separate transcriptional regulation. The transcription regulatory region consists of a CAP binding site, a promoter consensus sequence region, and an operator sequence. The three structural genes of the lac operon encode the enzymes -galactosidase (lacZ), permease (lacY), and transacetylase (lacA). (b) The DNA sequence of the regulatory region of the lac operon, including the −10 and −35 consensus sequences, the operator, and the CAP binding site(a) The repressor protein (lacI) is encoded by a 1040-bp segment under separate transcriptional regulation. The transcription regulatory region consists of a CAP binding site, a promoter consensus sequence region, and an operator sequence. The three structural genes of the lac operon encode the enzymes -galactosidase (lacZ), permease (lacY), and transacetylase (lacA). (b) The DNA sequence of the regulatory region of the lac operon, including the −10 and −35 consensus sequences, the operator, and the CAP binding site

Lactose operon i—l—l Regulatory Repressor region Structural gene region \ \ —70 —60 —50 -40 -30 —20 —1 0 +1 +10 +20 +30 5’ 3, 3’ — 5’ l—i—' —35 sequence —10 sequence CAP—CAMP binding region gi—I—i—%i—l—i—%l—l—J Repressor CAP binding site Promoter (lacP) Operator (IacO) (lacZ) (lacl) I 00 O 1251 bp 609 bp lacl promoter ,’ CAP Operator \\\ 1’ binding \‘\\ / . \\ I, Slte \\\ / lac operon ‘\\ // promoter ‘\\\\ // \\‘\ // ‘\\ (b) ,/ \\ // Promoter region ‘\\\ / F——————————————————————————L————————————————————————————1 ‘\\\ // CAP binding site Promoter sequence Operator \\\\ — '5 4.. (U E Shine—Dalgamop . mRNA sequence 0 c. *5; i I“ H—. E e 2 j—Glu j—Ser J—Gly j—Gln