کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2185549 1095991 2010 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Crystal Structure of the Cyanobacterial Signal Transduction Protein PII in Complex with PipX
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی بیولوژی سلول
پیش نمایش صفحه اول مقاله
Crystal Structure of the Cyanobacterial Signal Transduction Protein PII in Complex with PipX
چکیده انگلیسی

PII proteins are highly conserved signal transducers in bacteria, archaea, and plants. They have a large flexible loop (T-loop) that adopts different conformations after covalent modification or binding to different effectors to regulate the functions of diverse protein partners. The PII partner PipX (PIIinteraction protein X), first identified from Synechococcus sp. PCC 7942, exists uniquely in cyanobacteria. PipX also interacts with the cyanobacterial global nitrogen regulator NtcA. The mutually exclusive binding of PII and NtcA by PipX in a 2-oxoglutarate (2-OG)-dependent manner enables PII to indirectly regulate the transcriptional activity of NtcA. However, the structural basis for these exclusive interactions remains unknown. We solved the crystal structure of the PII–PipX complex from the filamentous cyanobacterium Anabaena sp. PCC 7120 at 1.90 Å resolution. A homotrimeric PII captures three subunits of PipX through the T-loops. Similar to PII from Synechococcus, the core structure consists of an antiparallel β-sheet with four β-strands and two α-helices at the lateral surface. PipX adopts a novel structure composed of five twisted antiparallel β-strands and two α-helices, which is reminiscent of the PII structure. The T-loop of each PII subunit extends from the core structure as an antenna that is stabilized at the cleft between two PipX monomers via hydrogen bonds. In addition, the interfaces between the β-sheets of PipX and PII core structures partially contribute to complex formation. Comparative structural analysis indicated that PipX and 2-OG share a common binding site that overlaps with the 14 signature residues of cyanobacterial PII proteins. Our structure of PipX and the recently solved NtcA structure enabled us to propose a putative model for the NtcA–PipX complex. Taken together, these findings provide structural insights into how PII regulates the transcriptional activity of NtcA via PipX upon accumulation of the metabolite 2-OG.

Graphical AbstractFigure optionsDownload high-quality image (126 K)Download as PowerPoint slideResearch Highlights
► The PII trimer forms a complex with three PipX molecules.
► PipX and 2-oxoglutarate share the same binding site on the T-loop of PII.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Biology - Volume 402, Issue 3, 24 September 2010, Pages 552–559
نویسندگان
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