Influence of l-Leucine and l-Alanine on Lrp Regulation of foo, Coding for F1651, a Pap Homologue

ABSTRACT The foo operon encodes F1651 fimbriae that belong to the P-regulatory family and are synthesized by septicemic Escherichia coli. Using an Lrp-deficient host and the lrp gene cloned under the arabinose pBAD promoter, we demonstrated that foo was transcribed proportionally to the amount of Lrp synthesized. l-Leucine and l-alanine decreased drastically the steady-state transcription of foo and modified phase variation, independently of the presence of FooI. Specific mutations in the C-terminal region of Lrp reduced or abolished the repressive effect of these amino acids, indicating that they modulate F1651 by affecting Lrp.

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Effect of some D-amino acids on the steady-state level of glutamine synthetase in Escherichia coli.

Journal of Bacteriology ◽

10.1128/jb.163.3.1109-1113.1985 ◽

1985 ◽

Vol 163 (3) ◽

pp. 1109-1113

Author(s):

M A Berberich

Keyword(s):

Escherichia Coli ◽

Amino Acids ◽

Steady State ◽

Glutamine Synthetase ◽

State Level ◽

Steady State Level

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Molecular Characterization of the Mycoplasma gallisepticum pvpA Gene Which Encodes a Putative Variable Cytadhesin Protein

Infection and Immunity ◽

10.1128/iai.68.7.3956-3964.2000 ◽

2000 ◽

Vol 68 (7) ◽

pp. 3956-3964 ◽

Cited By ~ 57

Author(s):

S. Boguslavsky ◽

D. Menaker ◽

I. Lysnyansky ◽

T. Liu ◽

S. Levisohn ◽

...

Keyword(s):

Amino Acids ◽

Stop Codon ◽

Size Variation ◽

Phase Variation ◽

Mycoplasma Genitalium ◽

Mycoplasma Gallisepticum ◽

Terminal Region ◽

Repeated Sequences ◽

Human Pathogens ◽

Variable Surface

ABSTRACT A putative cytadhesin-related protein (PvpA) undergoing variation in its expression was identified in the avian pathogen Mycoplasma gallisepticum. The pvpA gene was cloned, expressed inEscherichia coli, and sequenced. It exhibits 54 and 52% homology with the P30 and P32 cytadhesin proteins of the human pathogens Mycoplasma pneumoniae and Mycoplasma genitalium, respectively. In addition, 50% homology was found with the MGC2 cytadhesin of M. gallisepticum and 49% homology was found with a stretch of 205 amino acids of the cytadherence accessory protein HMW3 of M. pneumoniae. The PvpA molecule possesses a proline-rich carboxy-terminal region (28%) containing two identical directly repeated sequences of 52 amino acids and a tetrapeptide motif (Pro-Arg-Pro-X) which is repeated 14 times. Genetic analysis of several clonal isolates representing different expression states of the PvpA product ruled out chromosomal rearrangement as the mechanism for PvpA phase variation. The molecular basis of PvpA variation was revealed in a short tract of repeated GAA codons, encoding five successive glutamate resides, located in the N-terminal region and subject to frequent mutation generating an in-frame UAA stop codon. Size variation of the PvpA protein was observed among M. gallisepticum strains, ranging from 48 to 55 kDa and caused by several types of deletions occurring at the PvpA C-terminal end and within the two directly repeated sequences. By immunoelectron microscopy, the PvpA protein was localized on the mycoplasma cell surface, in particular on the terminal tip structure. Collectively, these findings suggest that PvpA is a newly identified variable surface cytadhesin protein of M. gallisepticum.

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The eag domain regulates hERG channel inactivation gating via a direct interaction

The Journal of General Physiology ◽

10.1085/jgp.201210870 ◽

2013 ◽

Vol 141 (2) ◽

pp. 229-241 ◽

Cited By ~ 32

Author(s):

Ahleah S. Gustina ◽

Matthew C. Trudeau

Keyword(s):

Amino Acids ◽

Steady State ◽

Direct Interaction ◽

Terminal Region ◽

Herg Channel ◽

Channel Inactivation ◽

Large N ◽

Recovery From Inactivation ◽

Steady State Inactivation ◽

Resurgent Current

Human ether-á-go-go (eag)-related gene (hERG) potassium channel kinetics are characterized by rapid inactivation upon depolarization, along with rapid recovery from inactivation and very slow closing (deactivation) upon repolarization. These factors combine to create a resurgent hERG current, where the current amplitude is paradoxically larger with repolarization than with depolarization. Previous data showed that the hERG N-terminal eag domain regulated deactivation kinetics by making a direct interaction with the C-terminal region of the channel. A primary mechanism for fast inactivation depends on residues in the channel pore; however, inactivation was also shown to be slower after deletion of a large N-terminal region. The mechanism for N-terminal region regulation of inactivation is unclear. Here, we investigated the contributions of the large N-terminal domains (amino acids 1–354), including the eag domain (amino acids 1–135), to hERG channel inactivation kinetics and steady-state inactivation properties. We found that N-deleted channels lacking just the eag domain (Δ2–135) or both the eag domain and the adjacent proximal domain (Δ2–354) had less rectifying current–voltage (I-V) relationships, slower inactivation, faster recovery from inactivation, and lessened steady-state inactivation. We coexpressed genetically encoded N-terminal fragments for the eag domain (N1–135) or the eag domain plus the proximal domain (N1–354) with N-deleted hERG Δ2–135 or hERG Δ2–354 channels and found that the resulting channels had more rectifying I-V relationships, faster inactivation, slower recovery from inactivation, and increased steady-state inactivation, similar to those properties measured for wild-type (WT) hERG. We also found that the eag domain–containing fragments regulated the time to peak and the voltage at the peak of a resurgent current elicited with a ramp voltage protocol. The eag domain–containing fragments effectively converted N-deleted channels into WT-like channels. Neither the addition of the proximal domain to the eag domain in N1–354 fragments nor the presence of the proximal domain in hERG Δ2–135 channels measurably affected inactivation properties; in contrast, the proximal region regulated steady-state activation in hERG Δ2–135 channels. The results show that N-terminal region-dependent regulation of channel inactivation and resurgent current properties are caused by a direct interaction of the eag domain with the rest of the hERG channel.

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Escherichia coli Physiology in Luria-Bertani Broth

Journal of Bacteriology ◽

10.1128/jb.01368-07 ◽

2007 ◽

Vol 189 (23) ◽

pp. 8746-8749 ◽

Cited By ~ 546

Author(s):

Guennadi Sezonov ◽

Danièle Joseleau-Petit ◽

Richard D'Ari

Keyword(s):

Escherichia Coli ◽

Amino Acids ◽

Growth Rate ◽

Steady State ◽

Cell Mass ◽

Carbon Sources ◽

Luria Bertani ◽

E Coli ◽

Luria Bertani Broth ◽

State Growth

ABSTRACT Luria-Bertani broth supports Escherichia coli growth to an optical density at 600 nm (OD600) of 7. Surprisingly, however, steady-state growth ceases at an OD600 of 0.3, when the growth rate slows down and cell mass decreases. Growth stops for lack of a utilizable carbon source. The carbon sources for E. coli in Luria-Bertani broth are catabolizable amino acids, not sugars.

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