Rational Design and Synthesis of Novel Acadesine-Like Modulators of AMPK

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c omple x, ma de up of thre e short α -he lic e s, binds on the opposite surfa c e of the
c a ta lytic c le ft of the α -KD. More so, upon the binding of AMP a “ re gula tory spine ”
of four hydrophobic re sidue s, una ligne d in the ina c tive c onforma tion, be c ome s
sta c ke d in a lignme nt a llowing the a c tive site to be c orre c tly dispose d for a c tivity.
T he α -AID c onne c ts to the C -te rmina l doma in (α -C T D) through a n α -linke r re gion
tha t wra ps a round the γ subunit a nd is e sse ntia l for the a c tiva tion me c ha nism. T he
α -C T D is a sma ll globula r doma in, ric h in Se rine /T hre onine 50-re sidue se que nc e s
te rme d ST loops, a nd it inte ra c ts with the c ore of AMPK, the β-C T D whic h bridge s
the α a nd γ subunits.
2. T he β subunit c onta ins two highly c onse rve d doma ins: the c e ntra l c a rbohydra te
binding module (β –C B M) a nd the β-C T D. T he β-C B M is a me mbe r of a fa mily of
c a rbohydra te -binding module s (C B M) found in isoa myla se s a nd glyc oge n-
bra nc hing e nz yme s. In AMPK, it a llows a portion of the c e llula r e nz yme to bind to
glyc oge n pa rtic le s, e spe c ia lly in the c a se of isoforms with the β2 subunit whic h
displa ys highe r a ffinity for glyc oge n tha n β1 a nd is e xpre sse d in ske le ta l musc le
whe re glyc oge n c onte nt is ve ry high. E ve n so, only a portion of the e nz yme is
bound to the c a rbohydra te , whic h in the c a se of β1 de pe nds on a n a uto
phosphoryla tion of T hr148 in the β-C B M, by the e nz yme whic h pre ve nts binding.
T he role e na c te d by the β-C B M is still unc e rta in though sinc e glyc oge n syntha se is
a physiologic a l ta rge t of AMPK it ma y be use d to c o-loc a liz e AMPK with its
substra te . Inte re stingly the c le ft be twe e n β-C B M a nd the N-te rminus α -KD is a
binding site for the c la ss of a c tiva tors of AMPK inc luding A-769662 a nd
sa lic yla te s.
3. Fina lly, the γ subunit c onta in a t the ir C -te rmina l e nd four ta nde m re pe a ts known a s
c ysta thione β syntha se (C B S 1 to 4) tha t in most othe r C B S-c onta ining prote ins
a sse mble two by two in struc ture s known a s B a te ma n doma ins whic h c a n bind
liga nds c onta ining a de nosine , suc h a s AMP, ADP, AT P or S-a de nosylme thionine .
T he pe c ulia rity of AMPK is tha t inste a d of the norma l two C B S re pe a ts tha t
a sse mble to ma ke one B a te ma n doma in it ha s four thus forming two B a te ma n