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PDBsum entry 1hdf
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Structural protein
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PDB id
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1hdf
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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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Crystal structure of the calcium-Loaded spherulin 3a dimer sheds light on the evolution of the eye lens betagamma-Crystallin domain fold.
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Authors
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N.J.Clout,
M.Kretschmar,
R.Jaenicke,
C.Slingsby.
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Ref.
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Structure, 2001,
9,
115-124.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: The betagamma-crystallins belong to a superfamily of two-domain
proteins found in vertebrate eye lenses, with distant relatives occurring in
microorganisms. It has been considered that an eukaryotic stress protein,
spherulin 3a, from the slime mold Physarum polycephalum shares a common
one-domain ancestor with crystallins, similar to the one-domain 3-D structure
determined by NMR. RESULTS: The X-ray structure of spherulin 3a shows it to be a
tight homodimer, which is consistent with ultracentrifugation studies. The
(two-motif) domain fold contains a pair of calcium binding sites very similar to
those found in a two-domain prokaryotic betagamma-crystallin fold family member,
Protein S. Domain pairing in the spherulin 3a dimer is two-fold symmetric, but
quite different in character from the pseudo-two-fold pairing of domains in
betagamma-crystallins. There is no evidence that the spherulin 3a single domain
can fold independently of its partner domain, a feature that may be related to
the absence of a tyrosine corner. CONCLUSION: Although it is accepted that the
vertebrate two-domain betagamma-crystallins evolved from a common one-domain
ancestor, the mycetezoan single-domain spherulin 3a, with its unique mode of
domain pairing, is likely to be an evolutionary offshoot, perhaps from as far
back as the one-motif ancestral stage. The spherulin 3a protomer stability
appears to be dependent on domain pairing. Spherulin-like domain sequences that
are found within bacterial proteins associated with virulence are likely to bind
calcium.
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Figure 6.
Figure 6. The Extensive Hydrophobic Interface Between
Domains of the Spherulin s3a HomodimerThe appended side chains
are listed in Table 1
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The above figure is
reprinted
by permission from Cell Press:
Structure
(2001,
9,
115-124)
copyright 2001.
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