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PDBsum entry 2v5h
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Transcription
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PDB id
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2v5h
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Contents |
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(+ 0 more)
284 a.a.
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(+ 0 more)
111 a.a.
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References listed in PDB file
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Key reference
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Title
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The crystal structure of the complex of pii and acetylglutamate kinase reveals how pii controls the storage of nitrogen as arginine.
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Authors
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J.L.Llácer,
A.Contreras,
K.Forchhammer,
C.Marco-Marín,
F.Gil-Ortiz,
R.Maldonado,
I.Fita,
V.Rubio.
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Ref.
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Proc Natl Acad Sci U S A, 2007,
104,
17644-17649.
[DOI no: ]
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PubMed id
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Abstract
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Photosynthetic organisms can store nitrogen by synthesizing arginine, and,
therefore, feedback inhibition of arginine synthesis must be relieved in these
organisms when nitrogen is abundant. This relief is accomplished by the binding
of the PII signal transduction protein to acetylglutamate kinase (NAGK), the
controlling enzyme of arginine synthesis. Here, we describe the crystal
structure of the complex between NAGK and PII of Synechococcus elongatus, at
2.75-A resolution. We prove the physiological relevance of the observed
interactions by site-directed mutagenesis and functional studies. The complex
consists of two polar PII trimers sandwiching one ring-like hexameric NAGK (a
trimer of dimers) with the threefold axes of these molecules aligned. The
binding of PII favors a narrow ring conformation of the NAGK hexamer that is
associated with arginine sites having low affinity for this inhibitor. Each PII
subunit contacts one NAGK subunit only. The contacts map in the inner
circumference of the NAGK ring and involve two surfaces of the PII subunit. One
surface is on the PII body and interacts with the C-domain of the NAGK subunit,
helping widen the arginine site found on the other side of this domain. The
other surface is at the distal region of a protruding large loop (T-loop) that
presents a novel compact shape. This loop is inserted in the interdomain crevice
of the NAGK subunit, contacting mainly the N-domain, and playing key roles in
anchoring PII on NAGK, in activating NAGK, and in complex formation regulation
by MgATP, ADP, 2-oxoglutarate, and by phosphorylation of serine-49.
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Figure 1.
Fig. 1. P[II]–NAGK complex. NAGK, P[II], and NAG are
shown as surface, ribbons, and spheres, respectively. NAGK
dimers and P[II] subunits are colored independently. Views are
along the threefold axis (A) or the twofold axis (B).
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Figure 2.
Fig. 2. P[II] subunit–NAGK subunit contacts. P[II], NAGK,
and NAG are shown as strings, ribbons, and spheres,
respectively. The contacting parts of the T-loop, B-loop, and
 1–
 1
connection, including some interacting side chains (in sticks),
are blue, red, and green, respectively. The surfaces provided by
these elements form meshworks of the same colors. The NAGK
central -sheet is green, and
other -strands and the -helices
are brownish and grayish for N- and C-domains, respectively.
Some NAGK elements and P[II] residues are labeled. (Inset)
Structure of bound NAG, encased within its electron density omit
map contoured at 2.5  .
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