Sandbox Reserved 828: Difference between revisions

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[http://jenalib.fli-leibniz.de/ImgLibPDB/thumbnail/manual/1ab4.pdb1_small.gif Biological Unit]
[http://jenalib.fli-leibniz.de/ImgLibPDB/thumbnail/manual/1ab4.pdb1_small.gif Biological Unit]


The gyrase structure reveals a dimer contact with a grooved concave surface for binding the G segment and a cluster of conserved charged residues surrounding the active-site tyrosines.
'''The A protein''' breaks and religates DNA as the DNA cleavage core and the CTD lies on it.  
The A protein breaks and religates DNA as the DNA cleavage core and the CTD lies on it. '''GyrA59 is the minimal fragment of the A-subunit which, when complexed with the B-subunit, has DNA-cleavage activity.''' The carboxy-terminal domain of GyrA is required for the introduction of DNA supercoils. Each GyrA59 monomer is composed of two domains at the head region: one similar to the DNA-binding domain of the catabolite-activator protein (CAP), including the helix–turn–helix (HTH) motif; and a second domain with α/β structure (the ‘tower’ domain) and a single domain with a helical core at the tail region. Two long helices (α14 and α18) emanate from this core and connect, together with the C-terminal helix (α19), the head and tail fragments The three connecting helices (α14,α18 and α19) adopt very different conformations, leading to large quaternary movements involving a single hinge-point within the helices and rigid body movements of the head fragments (Fig. 2d).. The tail is structurally conserved  although large surface loops emanating from different points give it a different outward appearance
The gyrA 59kDa N-ter domain is called Breakage and reunion domain  It is composed of two domains at the head region : a winged-helix-turn-helix domain or winged helix domain (WHD) where lies the catalytic tyrosines and a tower domain with alpha/beta structure.
And a single domain with a helical core at the tail region. Two long helices (a14 anda18) emanate from this core and connect, together with the C-terminal helix (a19), the head and tail fragments.
The three connecting helices (a14,a18 anda19) adopt very different conformations, leading to large quaternary movements involving a single hinge-point within the helices and rigid body movements of  
the head fragments .  
The tail is structurally conserved  although large surface loops emanating from different points give it a different outward appearance It forms a heart-shaped homodimer with two protein interfaces, the DNA- and C-gates. GyrA59 is the minimal fragment of the A-subunit which, when complexed with the B-subunit, has DNA-cleavage activity.
The remaining 30–35 kDa comprising the C-terminal domain (CTD) of GyrA shows a domain forming a b-pinwheel with a positively charged amino-acid perimeter. This carboxy-terminal domain of GyrA (cyan) is required for the introduction of DNA supercoils).
 


The B protein has the ATPase domain and the Toprim fold on it. Two ATPase domains dimerize to form a closed conformation. The Toprim fold is a Rossmann fold that contains three invariant acidic residues that coordinate magnesium ions involved in DNA cleavage and DNA religation
The B protein has the ATPase domain and the Toprim fold on it. Two ATPase domains dimerize to form a closed conformation. The Toprim fold is a Rossmann fold that contains three invariant acidic residues that coordinate magnesium ions involved in DNA cleavage and DNA religation
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