Biophysical and Biochemical Characterization of TP0037, a <sc>d</sc>-Lactate Dehydrogenase, Supports an Acetogenic Energy Conservation Pathway in <named-content content-type="genus-species">Treponema pallidum</named-content>

ABSTRACT A longstanding conundrum in Treponema pallidum biology concerns how the spirochete generates sufficient energy to fulfill its complex pathogenesis processes during human syphilitic infection. For decades, it has been assumed that the bacterium relies solely on glucose catabolism (via glycol...

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Autores principales:	Ranjit K. Deka, Wei Z. Liu, Michael V. Norgard, Chad A. Brautigam
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	d-lactate dehydrogenase Treponema pallidum X-ray crystallography acetogenesis spirochetes Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/3a0b4a869ea6444fb322654ec30c2a83
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spelling	oai:doaj.org-article:3a0b4a869ea6444fb322654ec30c2a832021-11-15T16:19:07ZBiophysical and Biochemical Characterization of TP0037, a <sc>d</sc>-Lactate Dehydrogenase, Supports an Acetogenic Energy Conservation Pathway in <named-content content-type="genus-species">Treponema pallidum</named-content>10.1128/mBio.02249-202150-7511https://doaj.org/article/3a0b4a869ea6444fb322654ec30c2a832020-10-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.02249-20https://doaj.org/toc/2150-7511ABSTRACT A longstanding conundrum in Treponema pallidum biology concerns how the spirochete generates sufficient energy to fulfill its complex pathogenesis processes during human syphilitic infection. For decades, it has been assumed that the bacterium relies solely on glucose catabolism (via glycolysis) for generation of its ATP. However, the organism’s robust motility, believed to be essential for human tissue invasion and dissemination, would require abundant ATP likely not provided by the parsimony of glycolysis. As such, additional ATP generation, either via a chemiosmotic gradient, substrate-level phosphorylation, or both, likely exists in T. pallidum. Along these lines, we have hypothesized that T. pallidum exploits an acetogenic energy conservation pathway that relies on the redox chemistry of flavins. Central to this hypothesis is the apparent existence in T. pallidum of an acetogenic pathway for the conversion of d-lactate to acetate. Herein we have characterized the structural, biophysical, and biochemical properties of the first enzyme (d-lactate dehydrogenase [d-LDH]; TP0037) predicted in this pathway. Binding and enzymatic studies showed that recombinant TP0037 consumed d-lactate and NAD+ to produce pyruvate and NADH. The crystal structure of TP0037 revealed a fold similar to that of other d-acid dehydrogenases; residues in the cofactor-binding and active sites were homologous to those of other known d-LDHs. The crystal structure and solution biophysical experiments revealed the protein’s propensity to dimerize, akin to other d-LDHs. This study is the first to elucidate the enzymatic properties of T. pallidum’s d-LDH, thereby providing new compelling evidence for a flavin-dependent acetogenic energy conservation (ATP-generating) pathway in T. pallidum. IMPORTANCE Because T. pallidum lacks a Krebs cycle and the capability for oxidative phosphorylation, historically it has been difficult to reconcile how the syphilis spirochete generates sufficient ATP to fulfill its energy needs, particularly for its robust motility, solely from glycolysis. We have postulated the existence in T. pallidum of a flavin-dependent acetogenic energy conservation pathway that would generate additional ATP for T. pallidum bioenergetics. In the proposed acetogenic pathway, first d-lactate would be converted to pyruvate. Pyruvate would then be metabolized to acetate in three additional steps, with ATP being generated via substrate-level phosphorylation. This study provides structural, biochemical, and biophysical evidence for the first T. pallidum enzyme in the pathway (TP0037; d-lactate dehydrogenase) requisite for the conversion of d-lactate to pyruvate. The findings represent the first experimental evidence to support a role for an acetogenic energy conservation pathway that would contribute to nonglycolytic ATP production in T. pallidum.Ranjit K. DekaWei Z. LiuMichael V. NorgardChad A. BrautigamAmerican Society for Microbiologyarticled-lactate dehydrogenaseTreponema pallidumX-ray crystallographyacetogenesisspirochetesMicrobiologyQR1-502ENmBio, Vol 11, Iss 5 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	d-lactate dehydrogenase Treponema pallidum X-ray crystallography acetogenesis spirochetes Microbiology QR1-502
spellingShingle	d-lactate dehydrogenase Treponema pallidum X-ray crystallography acetogenesis spirochetes Microbiology QR1-502 Ranjit K. Deka Wei Z. Liu Michael V. Norgard Chad A. Brautigam Biophysical and Biochemical Characterization of TP0037, a <sc>d</sc>-Lactate Dehydrogenase, Supports an Acetogenic Energy Conservation Pathway in <named-content content-type="genus-species">Treponema pallidum</named-content>
description	ABSTRACT A longstanding conundrum in Treponema pallidum biology concerns how the spirochete generates sufficient energy to fulfill its complex pathogenesis processes during human syphilitic infection. For decades, it has been assumed that the bacterium relies solely on glucose catabolism (via glycolysis) for generation of its ATP. However, the organism’s robust motility, believed to be essential for human tissue invasion and dissemination, would require abundant ATP likely not provided by the parsimony of glycolysis. As such, additional ATP generation, either via a chemiosmotic gradient, substrate-level phosphorylation, or both, likely exists in T. pallidum. Along these lines, we have hypothesized that T. pallidum exploits an acetogenic energy conservation pathway that relies on the redox chemistry of flavins. Central to this hypothesis is the apparent existence in T. pallidum of an acetogenic pathway for the conversion of d-lactate to acetate. Herein we have characterized the structural, biophysical, and biochemical properties of the first enzyme (d-lactate dehydrogenase [d-LDH]; TP0037) predicted in this pathway. Binding and enzymatic studies showed that recombinant TP0037 consumed d-lactate and NAD+ to produce pyruvate and NADH. The crystal structure of TP0037 revealed a fold similar to that of other d-acid dehydrogenases; residues in the cofactor-binding and active sites were homologous to those of other known d-LDHs. The crystal structure and solution biophysical experiments revealed the protein’s propensity to dimerize, akin to other d-LDHs. This study is the first to elucidate the enzymatic properties of T. pallidum’s d-LDH, thereby providing new compelling evidence for a flavin-dependent acetogenic energy conservation (ATP-generating) pathway in T. pallidum. IMPORTANCE Because T. pallidum lacks a Krebs cycle and the capability for oxidative phosphorylation, historically it has been difficult to reconcile how the syphilis spirochete generates sufficient ATP to fulfill its energy needs, particularly for its robust motility, solely from glycolysis. We have postulated the existence in T. pallidum of a flavin-dependent acetogenic energy conservation pathway that would generate additional ATP for T. pallidum bioenergetics. In the proposed acetogenic pathway, first d-lactate would be converted to pyruvate. Pyruvate would then be metabolized to acetate in three additional steps, with ATP being generated via substrate-level phosphorylation. This study provides structural, biochemical, and biophysical evidence for the first T. pallidum enzyme in the pathway (TP0037; d-lactate dehydrogenase) requisite for the conversion of d-lactate to pyruvate. The findings represent the first experimental evidence to support a role for an acetogenic energy conservation pathway that would contribute to nonglycolytic ATP production in T. pallidum.
format	article
author	Ranjit K. Deka Wei Z. Liu Michael V. Norgard Chad A. Brautigam
author_facet	Ranjit K. Deka Wei Z. Liu Michael V. Norgard Chad A. Brautigam
author_sort	Ranjit K. Deka
title	Biophysical and Biochemical Characterization of TP0037, a <sc>d</sc>-Lactate Dehydrogenase, Supports an Acetogenic Energy Conservation Pathway in <named-content content-type="genus-species">Treponema pallidum</named-content>
title_short	Biophysical and Biochemical Characterization of TP0037, a <sc>d</sc>-Lactate Dehydrogenase, Supports an Acetogenic Energy Conservation Pathway in <named-content content-type="genus-species">Treponema pallidum</named-content>
title_full	Biophysical and Biochemical Characterization of TP0037, a <sc>d</sc>-Lactate Dehydrogenase, Supports an Acetogenic Energy Conservation Pathway in <named-content content-type="genus-species">Treponema pallidum</named-content>
title_fullStr	Biophysical and Biochemical Characterization of TP0037, a <sc>d</sc>-Lactate Dehydrogenase, Supports an Acetogenic Energy Conservation Pathway in <named-content content-type="genus-species">Treponema pallidum</named-content>
title_full_unstemmed	Biophysical and Biochemical Characterization of TP0037, a <sc>d</sc>-Lactate Dehydrogenase, Supports an Acetogenic Energy Conservation Pathway in <named-content content-type="genus-species">Treponema pallidum</named-content>
title_sort	biophysical and biochemical characterization of tp0037, a <sc>d</sc>-lactate dehydrogenase, supports an acetogenic energy conservation pathway in <named-content content-type="genus-species">treponema pallidum</named-content>
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/3a0b4a869ea6444fb322654ec30c2a83
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Biophysical and Biochemical Characterization of TP0037, a <sc>d</sc>-Lactate Dehydrogenase, Supports an Acetogenic Energy Conservation Pathway in <named-content content-type="genus-species">Treponema pallidum</named-content>

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