Crystal Structures of Streptococcus mutans 2′-Deoxycytidylate Deaminase and Its Complex with Substrate Analog and Allosteric Regulator dCTP·Mg2+

cAMP is an evolutionary conserved, prototypic second messenger regulating numerous cellular functions. In mammals, cAMP is synthesized by one of 10 homologous adenylyl cyclases (ACs): nine transmembrane enzymes and one soluble AC (sAC). Among these, only sAC is directly activated by bicarbonate (HCO3−); it thereby serves as a cellular sensor for HCO3−, carbon dioxide (CO2), and pH in physiological functions, such as sperm activation, aqueous humor formation, and metabolic regulation. Here, we describe crystal structures of human sAC catalytic domains in the apo state and in complex with substrate analog, products, and regulators. The activator HCO3− binds adjacent to Arg176, which acts as a switch that enables formation of the catalytic cation sites. An anionic inhibitor, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid, inhibits sAC through binding to the active site entrance, which blocks HCO3− activation through steric hindrance and trapping of the Arg176 side chain. Finally, product complexes reveal small, local rearrangements that facilitate catalysis. Our results provide a molecular mechanism for sAC catalysis and cellular HCO3− sensing and a basis for targeting this system with drugs.

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Open–closed conformational change revealed by the crystal structures of 3-keto-l-gulonate 6-phosphate decarboxylase from Streptococcus mutans

Biochemical and Biophysical Research Communications ◽

10.1016/j.bbrc.2009.02.049 ◽

2009 ◽

Vol 381 (3) ◽

pp. 429-433 ◽

Cited By ~ 1

Author(s):

Gui-Lan Li ◽

Xiang Liu ◽

Jie Nan ◽

Erik Brostromer ◽

Lan-Fen Li ◽

...

Keyword(s):

Crystal Structures ◽

Conformational Change ◽

Streptococcus Mutans

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Crystal structures of substrate & substrate analog complexes of protocatechuate 3,4-dioxygenase yield mechanistic insights

Journal of Inorganic Biochemistry ◽

10.1016/0162-0134(95)97465-3 ◽

1995 ◽

Vol 59 (2-3) ◽

pp. 367 ◽

Cited By ~ 4

Author(s):

Allen M. Orville ◽

Natesan Elango ◽

Douglas H. Ohlendorf ◽

John D. Lipscomb

Keyword(s):

Crystal Structures ◽

Substrate Analog

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Crystal Structures of Substrate and Substrate Analog Complexes of Protocatechuate 3,4-Dioxygenase: Endogenous Fe3+Ligand Displacement in Response to Substrate Binding†,‡

Biochemistry ◽

10.1021/bi970469f ◽

1997 ◽

Vol 36 (33) ◽

pp. 10052-10066 ◽

Cited By ~ 106

Author(s):

Allen M. Orville ◽

John D. Lipscomb ◽

Douglas H. Ohlendorf

Keyword(s):

Crystal Structures ◽

Substrate Binding ◽

Substrate Analog ◽

Ligand Displacement

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Pollutant Identification by Selected Area Electron Diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052675 ◽

1974 ◽

Vol 32 ◽

pp. 532-533

Author(s):

R. E. Ferrell ◽

G. G. Paulson ◽

C. W. Walker

Keyword(s):

Thermal Treatment ◽

Electron Diffraction ◽

Sample Preparation ◽

Crystal Structures ◽

Water Samples ◽

Environmental Samples ◽

Short Review ◽

Selected Area Electron Diffraction ◽

Multiple Component

Selected area electron diffraction (SAD) has been used successfully to determine crystal structures, identify traces of minerals in rocks, and characterize the phases formed during thermal treatment of micron-sized particles. There is an increased interest in the method because it has the potential capability of identifying micron-sized pollutants in air and water samples. This paper is a short review of the theory behind SAD and a discussion of the sample preparation employed for the analysis of multiple component environmental samples.

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The Imaging of Crystal Structures and Crystal Defects

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069995 ◽

1978 ◽

Vol 36 (3) ◽

pp. 207-217

Author(s):

J.M. Cowley

Keyword(s):

Electron Microscope ◽

Crystal Structures ◽

Phase Contrast ◽

Crystal Defects ◽

Atom Density ◽

Lack Of Information ◽

Spatial Frequencies

The problem of "understandinq" electron microscope imaqes becomes more acute as the resolution is improved. The naive interpretation of an imaqe as representinq the projection of an atom density becomes less and less appropriate. We are increasinqly forced to face the complexities of coherent imaqinq of what are essentially phase objects. Most electron microscopists are now aware that, for very thin weakly scatterinq objects such as thin unstained bioloqical specimens, hiqh resolution imaqes are best obtained near the optimum defocus, as prescribed by Scherzer, where the phase contrast imaqe qives a qood representation of the projected potential, apart from a lack of information on the lower spatial frequencies. But phase contrast imaqinq is never simple except in idealized limitinq cases.

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Cell Wall Ultrastructure in Three Strains of a Cariogenic Streptococcus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065730 ◽

1971 ◽

Vol 29 ◽

pp. 338-339

Author(s):

M. J. Kramer ◽

Alan L. Coykendall

Keyword(s):

Cell Wall ◽

Dental Caries ◽

Streptococcus Mutans ◽

Microscopic Study ◽

Electron Microscopic Study ◽

Genetic Heterogeneity ◽

Morphological Characteristics ◽

Electron Microscopic ◽

Dna Reassociation ◽

Wall Ultrastructure

During the almost 50 years since Streptococcus mutans was first suggested as a factor in the etiology of dental caries, a multitude of studies have confirmed the cariogenic potential of this organism. Streptococci have been isolated from human and animal caries on numerous occasions and, with few exceptions, they are not typable by the Lancefield technique but are relatively homogeneous in their biochemical reactions. An analysis of the guanine-cytosine (G-C) composition of the DNA from strains K-1-R, NCTC 10449, and FA-1 by one of us (ALC) revealed significant differences and DNA-DNA reassociation experiments indicated that genetic heterogeneity existed among the three strains. The present electron microscopic study had as its objective the elucidation of any distinguishing morphological characteristics which might further characterize the respective strains.

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