Redox and Light Control the Heme-Sensing Activity of AppA

ABSTRACT The DNA binding activity of the photosystem-specific repressor PpsR is known to be repressed by the antirepressor AppA. AppA contains a blue-light-absorbing BLUF domain and a heme-binding SCHIC domain that controls the interaction of AppA with PpsR in response to light and heme availability...

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Autores principales:	Liang Yin, Vladimira Dragnea, George Feldman, Loubna A. Hammad, Jonathan A. Karty, Charles E. Dann, Carl E. Bauer
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2013
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/98ea41444d3d44cfaedaf3ecea57476e
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spelling	oai:doaj.org-article:98ea41444d3d44cfaedaf3ecea57476e2021-11-15T15:42:47ZRedox and Light Control the Heme-Sensing Activity of AppA10.1128/mBio.00563-132150-7511https://doaj.org/article/98ea41444d3d44cfaedaf3ecea57476e2013-11-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00563-13https://doaj.org/toc/2150-7511ABSTRACT The DNA binding activity of the photosystem-specific repressor PpsR is known to be repressed by the antirepressor AppA. AppA contains a blue-light-absorbing BLUF domain and a heme-binding SCHIC domain that controls the interaction of AppA with PpsR in response to light and heme availability. In this study, we have solved the structure of the SCHIC domain and identified the histidine residue that is critical for heme binding. We also demonstrate that dark-adapted AppA binds heme better than light-excited AppA does and that heme bound to the SCHIC domain significantly reduces the length of the BLUF photocycle. We further show that heme binding to the SCHIC domain is affected by the redox state of a disulfide bridge located in the Cys-rich carboxyl-terminal region. These results demonstrate that light, redox, and heme are integrated inputs that control AppA’s ability to disrupt the DNA binding activity of PpsR. IMPORTANCE Photosynthetic bacteria must coordinate synthesis of the tetrapyrroles cobalamin, heme, and bacteriochlorophyll, as overproduction of the latter two is toxic to cells. A key regulator controlling tetrapyrrole biosynthesis is PpsR, and the activity of PpsR is controlled by the heme-binding and light-regulated antirepressor AppA. We show that AppA binds heme only under dark conditions and that heme binding significantly affects the length of the AppA photocycle. Since AppA interacts with PpsR only in the dark, bound heme thus stimulates the antirepressor activity of PpsR. This causes the redirection of tetrapyrrole biosynthesis away from heme into the bacteriochlorophyll branch.Liang YinVladimira DragneaGeorge FeldmanLoubna A. HammadJonathan A. KartyCharles E. DannCarl E. BauerAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 4, Iss 5 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Liang Yin Vladimira Dragnea George Feldman Loubna A. Hammad Jonathan A. Karty Charles E. Dann Carl E. Bauer Redox and Light Control the Heme-Sensing Activity of AppA
description	ABSTRACT The DNA binding activity of the photosystem-specific repressor PpsR is known to be repressed by the antirepressor AppA. AppA contains a blue-light-absorbing BLUF domain and a heme-binding SCHIC domain that controls the interaction of AppA with PpsR in response to light and heme availability. In this study, we have solved the structure of the SCHIC domain and identified the histidine residue that is critical for heme binding. We also demonstrate that dark-adapted AppA binds heme better than light-excited AppA does and that heme bound to the SCHIC domain significantly reduces the length of the BLUF photocycle. We further show that heme binding to the SCHIC domain is affected by the redox state of a disulfide bridge located in the Cys-rich carboxyl-terminal region. These results demonstrate that light, redox, and heme are integrated inputs that control AppA’s ability to disrupt the DNA binding activity of PpsR. IMPORTANCE Photosynthetic bacteria must coordinate synthesis of the tetrapyrroles cobalamin, heme, and bacteriochlorophyll, as overproduction of the latter two is toxic to cells. A key regulator controlling tetrapyrrole biosynthesis is PpsR, and the activity of PpsR is controlled by the heme-binding and light-regulated antirepressor AppA. We show that AppA binds heme only under dark conditions and that heme binding significantly affects the length of the AppA photocycle. Since AppA interacts with PpsR only in the dark, bound heme thus stimulates the antirepressor activity of PpsR. This causes the redirection of tetrapyrrole biosynthesis away from heme into the bacteriochlorophyll branch.
format	article
author	Liang Yin Vladimira Dragnea George Feldman Loubna A. Hammad Jonathan A. Karty Charles E. Dann Carl E. Bauer
author_facet	Liang Yin Vladimira Dragnea George Feldman Loubna A. Hammad Jonathan A. Karty Charles E. Dann Carl E. Bauer
author_sort	Liang Yin
title	Redox and Light Control the Heme-Sensing Activity of AppA
title_short	Redox and Light Control the Heme-Sensing Activity of AppA
title_full	Redox and Light Control the Heme-Sensing Activity of AppA
title_fullStr	Redox and Light Control the Heme-Sensing Activity of AppA
title_full_unstemmed	Redox and Light Control the Heme-Sensing Activity of AppA
title_sort	redox and light control the heme-sensing activity of appa
publisher	American Society for Microbiology
publishDate	2013
url	https://doaj.org/article/98ea41444d3d44cfaedaf3ecea57476e
work_keys_str_mv	AT liangyin redoxandlightcontrolthehemesensingactivityofappa AT vladimiradragnea redoxandlightcontrolthehemesensingactivityofappa AT georgefeldman redoxandlightcontrolthehemesensingactivityofappa AT loubnaahammad redoxandlightcontrolthehemesensingactivityofappa AT jonathanakarty redoxandlightcontrolthehemesensingactivityofappa AT charlesedann redoxandlightcontrolthehemesensingactivityofappa AT carlebauer redoxandlightcontrolthehemesensingactivityofappa
_version_	1718427601730535424

Redox and Light Control the Heme-Sensing Activity of AppA

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