Lambda Flashcards
the protein J of the lambda tail binds to apore on the surface which serves to bring maltose in; these pores are only expressed in the absence of glucose and presence of maltose–>so entrance of lambda depends on the nutritional condition e. coli is in
ya
early expression in lambda
initially Pl and Pr are expressed and Prm is not bc it is a weak promotor
what is cro’s purpose?
antirepressor; causes repression of the main lambda repressor; binds near Prm (repressor) and prevents expression of C1
what are the early genes?
N and cro
what is N’s role?
anti-termination factor which binds RNA (at the nut site)–>binding prevents intrinsic termination seqs from folding; sufficient N must be present to antiterminate; antitermination happens on both L and R transcripts
what are the late-early genes?
xis, int, cII and cIII, Q
left side makes genes required for genome integration (lysogeny); right side initially makes proteins which will lead to repressor production (lysogeny) and later for viral structural proteins:
what is xis?
excisionase for removal of lambda genome into e coli genome
what is int?
integrase–for insertion of lambda genome into e coli genome
what is cIII?
protein which protects cII from degradation by cellular proteases–basically, cIII amount determines cII amount which determines lysogeny or lysis; binds HflB–>protease for cII
what is cII?
transcription factor which recruits RNA pol to bind 3 additional weak promoters; a build up of this leads to lysogeny
what is Q?
another antiterminator needed to allow synthesis of RNA into genes for viral head and tail proteins; binds at qut, immediately after pR’
what is Pint?
integrase; more integrase = lambda will more readily insert its genome into e coli than it excises
what is Pre?
P repressor establishment–> produced mRNA that encodes the repressor cI (lambda repressor)–PRODUCES C1
what is PaQ?
produces a non-coding mRNA; both Pre and Paq produce an antisense RNA to cro, O, P, and Q–>reduces their transcription and translation
where is initial cI production?
through Pre promoter; once cI is in the cell it changes gene expression at the main control region–> sites 3, 2, and 1, between cI and cro; cI preferentially binds to site 1 and 2 which will block the promotor for cro and increase RNA pol binding to Prm
how does the cI protein do its job?
binds to right operator sites 1 and 2 as dimers; it also binds to left operator at sites 1 and 2; at this point, no more N, antitermination, and cI is the only lambda gene expressed; cI will cause the DNA to loop, so the cIs on the Ol and Or can octomerize; the binding of Cro at the weak consensus seqs Ol3 and Or3 to form a tetramer and cI will negatively regulate itself
integration of lambda–site specific, as the att site in the lambda genome is homologous to seq beside the galactose operon
ya
integrase is required to insert the lambda genome, but both int and excisionase are required to remove it
ya
