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PDBsum entry 1gmi
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Structure of the c2 domain from novel protein kinase cepsilon. A membrane binding model for ca(2+)-Independent c2 domains.
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Authors
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W.F.Ochoa,
J.Garcia-Garcia,
I.Fita,
S.Corbalan-Garcia,
N.Verdaguer,
J.C.Gomez-Fernandez.
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Ref.
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J Mol Biol, 2001,
311,
837-849.
[DOI no: ]
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PubMed id
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Abstract
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Protein kinase Cepsilon (PKCepsilon) is a member of the novel PKCs which are
activated by acidic phospholipids, diacylglycerol and phorbol esters, but lack
the calcium dependence of classical PKC isotypes. The crystal structures of the
C2 domain of PKCepsilon, crystallized both in the absence and in the presence of
the two acidic phospholipids, 1,2-dicaproyl-sn-phosphatidyl-l-serine (DCPS) and
1,2-dicaproyl-sn-phosphatidic acid (DCPA), have now been determined at 2.1, 1.7
and 2.8 A resolution, respectively. The central feature of the PKCepsilon-C2
domain structure is an eight-stranded, antiparallel, beta-sandwich with a type
II topology similar to that of the C2 domains from phospholipase C and from
novel PKCdelta. Despite the similar topology, important differences are found
between the structures of C2 domains from PKCs delta and epsilon, suggesting
they be considered as different PKC subclasses. Site-directed mutagenesis
experiments and structural changes in the PKCepsilon-C2 domain from crystals
with DCPS or DCPA indicate, though phospholipids were not visible in these
structures, that loops joining strands beta1-beta2 and beta5-beta6 participate
in the binding to anionic membranes. The different behavior in membrane-binding
and activation between PKCepsilon and classical PKCs appears to originate in
localized structural changes, which include a major reorganization of the region
corresponding to the calcium binding pocket in classical PKCs. A mechanism is
proposed for the interaction of the PKCepsilon-C2 domain with model membranes
that retains basic features of the docking of C2 domains from classical,
calcium-dependent, PKCs.
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Figure 4.
Figure 4. Top region of the C2-domain b-sandwich from PKCe.
(a) Superimposition of loops 1 and 3 from PKCe (magenta) with
the structurally equivalents loops CBR1 and CBR3 from the
Ca^2+-dependent C2 domain of PKCa (cyan). The two Ca ions
identified in the crystal structure of the C2 domain of PKCa are
depicted as green spheres. Three of the five aspartate residues
conserved in classical PKCs were replaced in PKCe by residues
Pro33, His85 and Ala87. The imidazole ring of His85 occupies the
position corresponding to the active Ca ion. (b) Superimposition
of loop 1 and loop 3 of PKCe onto the equivalent loops in PKCd.
The relative disposition of the loops and the orientation of the
side-chains within the pocket differs markedly between the two
novel PKCs.
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Figure 6.
Figure 6. (a) The docking of the PKCa-C2-Ca^2+-DCPS ternary
complex onto a model membrane and (b) the superimposition of the
structures from the PKCs C2 domains a and e suggest (c) a
docking mechanism for PKCe-C2. In this model only loop 3 appears
to penetrate into the lipid bilayer, though loop 1 would also be
in close contact with the membrane. In the model bulky
side-chains of Trp23, Ile89 and Tyr91 (explicitly depicted)
could reach the inner membrane while conserved basic residues
(particularly Arg26, Arg32, Arg50 and probably also His85) would
interact with the phospholipid charged heads (c). The
coordination of the Mg2+ might also facilitate the interaction
with the membrane (see the text). In this model the carboxy end
of the C2 domain, to be continued by the pseudo-substrate and
the C1 domain in the intact PKC, appears situated apart from the
membrane.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2001,
311,
837-849)
copyright 2001.
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