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Linkage between the bacterial acid stress and stringent responses: the structure of the inducible lysine decarboxylase
Author(s) -
Kanjee Usheer,
Gutsche Irina,
Alexopoulos Eftichia,
Zhao Boyu,
El Bakkouri Majida,
Thibault Guillaume,
Liu Kaiyin,
Ramachandran Shaliny,
Snider Jamie,
Pai Emil F,
Houry Walid A
Publication year - 2011
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2011.5
Subject(s) - lysine decarboxylase , biology , lysine , biochemistry , stringent response , escherichia coli , effector , enzyme , antiporter , amino acid , cadaverine , membrane , gene , putrescine
The Escherichia coli inducible lysine decarboxylase, LdcI/CadA, together with the inner‐membrane lysine‐cadaverine antiporter, CadB, provide cells with protection against mild acidic conditions (pH∼5). To gain a better understanding of the molecular processes underlying the acid stress response, the X‐ray crystal structure of LdcI was determined. The structure revealed that the protein is an oligomer of five dimers that associate to form a decamer. Surprisingly, LdcI was found to co‐crystallize with the stringent response effector molecule ppGpp, also known as the alarmone, with 10 ppGpp molecules in the decamer. ppGpp is known to mediate the stringent response, which occurs in response to nutrient deprivation. The alarmone strongly inhibited LdcI enzymatic activity. This inhibition is important for modulating the consumption of lysine in cells during acid stress under nutrient limiting conditions. Hence, our data provide direct evidence for a link between the bacterial acid stress and stringent responses.