Region ¾ linker of s lies in the middle of the RNA exit channel in the open complex

TLS Online TPP Program

#Id: 560

#Unit 2. Cellular Organization

When polymerase binding causes transition to the open complex and initiates transcription. This gives a low level of constitutive expression called the basal level. 

Binding of RNA polymerase is the rate-limiting step in this case.

TLS Online TPP Program

#Id: 561

#Unit 2. Cellular Organization

lacZ encodes for b-galactosidase, a tetramer of 500 kD. The enzyme breaks lactose is cleaved into glucose and galactose. This enzyme also produces an important byproduct, b-1,6-allolactase.

TLS Online TPP Program

#Id: 562

#Unit 2. Cellular Organization

The lac mRNA (as most mRNA is in bacteria) is extremely unstable and decays with a half-life of only 3 minutes.

TLS Online TPP Program

#Id: 563

#Unit 2. Cellular Organization

B-1,6-allolactase is a true inducer of Lac operon which activates Lac ZYA gene expression by inhibiting Lac Repressor

TLS Online TPP Program

#Id: 564

#Unit 2. Cellular Organization

Negative Regulation/ Positive Regulation or catabolic repression

TLS Online TPP Program

#Id: 565

#Unit 2. Cellular Organization

Molecules that induce enzyme synthesis but are not metabolized are called gratuitous inducers such as IPTG