MICR 302 Lecture Notes - Lecture 4: Guanosine Pentaphosphate, Stringent Response, Sigma Factor
16 Mar 2018
School
Department
Course
Professor
Document Summary
Ppgpp modi es the function of rnap by changing it"s choice of promoter and/or changing its a nity for alternative sigma factors. Modi ed nucleotide (guanine) with 2-3 phosphoryl groups. Accumulates in cells starved for amino acids. Other inducers include phosphate starvation and lack of a carbon source or fatty acids. Amino acid starvation: massive reduction in the synthesis of rrna and trna and reduces mrna synthesis. A reduced synthesis of nucleotides, carbohydrates, lipids, oct. Rela lacks functional hydrolase activity so only spot can break the alarmone. Rela and spot will induce (p)ppgpp formation under di erent conditions. The stringent response (alarmone) e ects a lot of di erent pathways. The presence of ppgpp will cause the rnap to bind to promoters for rpos and make sigma s, bind promoters for universal stress proteins, and promoters for amino acid proteosynthesis and proteolysis. Indirectly: via in uencing promoter binding and the choice of sigma.
