Give the comparisons of Rec-type (proteine) and Rec BCD Complex. What is the ro

Give the comparisons of Rec-type (proteine) and Rec BCD
Complex. What is the role of each?

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Give the comparisons of Rec-type (proteine) and Rec BCD Complex. What is the role of each?..

Answer / ntegerejimana theogene

RecBCD (EC 3.1.11.5, Exonuclease V, Escherichia coli
exonuclease V, E. coli exonuclease V, gene recBC endoenzyme,
RecBC deoxyribonuclease, gene recBC DNase, gene recBCD
enzymes) is an enzyme of the E. coli bacterium that
initiates recombinational repair from potentially lethal
double strand breaks in DNA which may result from ionizing
radiation, replication errors, endonucleases, oxidative
damage, and a host of other factors.[2][3] The RecBCD enzyme
is both a helicase that unwinds, or separates the strands of
DNA, and a nuclease that makes single-stranded nicks in DNA.[1]

Both the RecD and RecB subunits are helicases, i.e.,
energy-dependent molecular motors that unwind DNA (or RNA in
the case of other proteins). The RecB subunit in addition
has a nuclease function.[5] Finally, RecBCD enzyme (perhaps
the RecC subunit) recognizes a specific sequence in DNA,
5'-GCTGGTGG-3', known as Chi (sometimes designated with the
Greek letter χ).

RecBCD is unusual amongst helicases because it has two
helicases that travel with different rates[6] and because it
can recognize and be altered by the Chi DNA sequence.[7][8]
RecBCD avidly binds an end of linear double-stranded (ds)
DNA. The RecD helicase travels on the strand with a 5' end
at which the enzyme initiates unwinding, and RecB on the
strand with a 3' end. RecB is slower than RecD, so that a
single-stranded (ss) DNA loop accumulates ahead of RecB
(Figure 2). This produces DNA structures with two ss tails
(a shorter 3’ ended tail and a longer 5’ ended tail) and one
ss loop (on the 3' ended strand) observed by electron
microscopy.[9] The ss tails can anneal to produce a second
ss loop complementary to the first one; such twin-loop
structures were initially referred to as “rabbit ears.”

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