5O3S

Carbon regulatory PII-like protein SbtB from Synechocystis sp. 6803 in Apo state, hexagonal crystal form

Summary for 5O3S

• Entry DOI: 10.2210/pdb5o3s/pdb
• Descriptor: Membrane-associated protein slr1513 (2 entities in total)
• Functional Keywords: sbtb, carbon sensing, pii-like, cyanobacteria, signaling protein
• Biological source: Synechocystis sp. (strain PCC 6803 / Kazusa)
• Cellular location: Cellular thylakoid membrane ; Peripheral membrane protein ; Cytoplasmic side : P73954
• Total number of polymer chains: 1
• Total formula weight: 13222.11

Authors

Selim, K.A.,Albrecht, R.,Forchhammer, K.,Hartmann, M.D. (deposition date: 2017-05-24, release date: 2018-05-16, Last modification date: 2024-10-16)

Primary citation

Selim, K.A.,Haase, F.,Hartmann, M.D.,Hagemann, M.,Forchhammer, K.
PII-like signaling protein SbtB links cAMP sensing with cyanobacterial inorganic carbon response.
Proc. Natl. Acad. Sci. U.S.A., 115:E4861-E4869, 2018

PubMed Abstract: Cyanobacteria are phototrophic prokaryotes that evolved oxygenic photosynthesis ∼2.7 billion y ago and are presently responsible for ∼10% of total global photosynthetic production. To cope with the evolutionary pressure of dropping ambient CO concentrations, they evolved a CO-concentrating mechanism (CCM) to augment intracellular inorganic carbon (C) levels for efficient CO fixation. However, how cyanobacteria sense the fluctuation in C is poorly understood. Here we present biochemical, structural, and physiological insights into SbtB, a unique P-like signaling protein, which provides new insights into C sensing. SbtB is highly conserved in cyanobacteria and is coexpressed with CCM genes. The SbtB protein from the cyanobacterium sp. PCC 6803 bound a variety of adenosine nucleotides, including the second messenger cAMP. Cocrystal structures unraveled the individual binding modes of trimeric SbtB with AMP and cAMP. The nucleotide-binding pocket is located between the subunit clefts of SbtB, perfectly matching the structure of canonical P proteins. This clearly indicates that proteins of the P superfamily arose from a common ancestor, whose structurally conserved nucleotide-binding pocket has evolved to sense different adenyl nucleotides for various signaling functions. Moreover, we provide physiological and biochemical evidence for the involvement of SbtB in C acclimation. Collectively, our results suggest that SbtB acts as a C sensor protein via cAMP binding, highlighting an evolutionarily conserved role for cAMP in signaling the cellular carbon status.

PubMed: 29735650
DOI: 10.1073/pnas.1803790115

Experimental method

X-RAY DIFFRACTION (2.2 Å)