MIP 300 Lecture Notes - Anaerobic Respiration, Galactose, Inductor
25 Jun 2014
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Average protein ~300 aa in length; make one 380 aa long. 30 via aerobic respiration, >30 via anaerobic respiration. Don"t want proteins stop transcription or translation, usually transcription. Production of many catabolic enzymes controlled this way. A regulator gene produces repressor proteins which bind to operator, stops transcription. Inducer molecule increases transcription, binds to repressor protein, can"t bind operator. Example: b-galactosidase (b-gal) synthesis, lac operon b-gal: lactose glucose & galactose. When lactose is present, make enzymes to digest lactose. Lactose inactivates repressor protein (usually binds on operator) Production of biosynthetic enzymes controlled in this way (anabolism) Gene has regulatory region near promoter, called operator. A regulator gene produces repressor protein which is inactive, can"t bind operator. Corepressor molecule binds repressor protein, activating its ability to bind operator, decreases transcription. When histidine is present, don"t make enzymes to make histidine. Regulatory site effector molecules bind, alter active site. Enzyme activity altered by addition & removal of reversible covalent modifications, e. g. phosphorylation.
