scholarly journals Lysine Residues in the MK-Rich Region Are Not Required for Binding of the PbsP Protein From Group B Streptococci to Plasminogen

2021 ◽  
Vol 11 ◽  
Author(s):  
Francesco Coppolino ◽  
Letizia Romeo ◽  
Giampiero Pietrocola ◽  
Germana Lentini ◽  
Giuseppe Valerio De Gaetano ◽  
...  
Keyword(s):  
Binding Sites ◽  
Invasive Infection ◽  
Group B Streptococci ◽  
Rich Domain ◽  
Charged Amino Acids ◽  
Lysine Residues ◽  
Group B ◽  
Host Tissues ◽  
Positively Charged ◽  
Bacterial Sequence

Binding to plasminogen (Plg) enables bacteria to associate with and invade host tissues. The cell wall protein PbsP significantly contributes to the ability of group B streptococci, a frequent cause of invasive infection, to bind Plg. Here we sought to identify the molecular regions involved in the interactions between Plg and PbsP. The K4 Kringle domain of the Plg molecule was required for binding of Plg to whole PbsP and to a PbsP fragment encompassing a region rich in methionine and lysine (MK-rich domain). These interactions were inhibited by free L-lysine, indicating the involvement of lysine binding sites in the Plg molecule. However, mutation to alanine of all lysine residues in the MK-rich domain did not decrease its ability to bind Plg. Collectively, our data identify a novel bacterial sequence that can interact with lysine binding sites in the Plg molecule. Notably, such binding did not require the presence of lysine or other positively charged amino acids in the bacterial receptor. These data may be useful for developing alternative therapeutic strategies aimed at blocking interactions between group B streptococci and Plg.

scholarly journals One Intact Transmembrane Substrate Binding Site Is Sufficient for the Function of the Homodimeric Type I ATP-Binding Cassette Importer for Positively Charged Amino Acids Art(MP) 2 of Geobacillus stearothermophilus

2018 ◽  
Vol 200 (12) ◽  
Author(s):  
Johanna Heuveling ◽  
Heidi Landmesser ◽  
Erwin Schneider
Keyword(s):  
Binding Site ◽  
Binding Sites ◽  
Substrate Binding ◽  
Binding Pocket ◽  
Atp Binding ◽  
Content Type ◽  
Charged Amino Acids ◽  
Substrate Binding Sites ◽  
Positively Charged ◽  
Atp Binding Cassette

ABSTRACT ATP-binding cassette (ABC) transport systems comprise two transmembrane domains/subunits that form a translocation path and two nucleotide-binding domains/subunits that bind and hydrolyze ATP. Prokaryotic canonical ABC import systems require an extracellular substrate-binding protein for function. Knowledge of substrate-binding sites within the transmembrane subunits is scarce. Recent crystal structures of the ABC importer Art(QN) 2 for positively charged amino acids of Thermoanerobacter tengcongensis revealed the presence of one substrate molecule in a defined binding pocket in each of the transmembrane subunits, ArtQ (J. Yu, J. Ge, J. Heuveling, E. Schneider, and M. Yang, Proc Natl Acad Sci U S A 112:5243–5248, 2015, https://doi.org/10.1073/pnas.1415037112 ). This finding raised the question of whether both sites must be loaded with substrate prior to initiation of the transport cycle. To address this matter, we first explored the role of key residues that form the binding pocket in the closely related Art(MP) 2 transporter of Geobacillus stearothermophilus , by monitoring consequences of mutations in ArtM on ATPase and transport activity at the level of purified proteins embedded in liposomes. Our results emphasize that two negatively charged residues (E153 and D160) are crucial for wild-type function. Furthermore, the variant Art[M(L67D)P] 2 exhibited strongly impaired activities, which is why it was considered for construction of a hybrid complex containing one intact and one impaired substrate-binding site. Activity assays clearly revealed that one intact binding site was sufficient for function. To our knowledge, our study provides the first biochemical evidence on transmembrane substrate-binding sites of an ABC importer. IMPORTANCE Canonical prokaryotic ATP-binding cassette importers mediate the uptake of a large variety of chemicals, including nutrients, osmoprotectants, growth factors, and trace elements. Some also play a role in bacterial pathogenesis, which is why full understanding of their mode of action is of the utmost importance. One of the unsolved problems refers to the chemical nature and number of substrate binding sites formed by the transmembrane subunits. Here, we report that a hybrid amino acid transporter of G. stearothermophilus , encompassing one intact and one impaired transmembrane binding site, is fully competent in transport, suggesting that the binding of one substrate molecule is sufficient to trigger the translocation process.

scholarly journals Characterization of a Novel Leucine-Rich Repeat Protein Antigen from Group B Streptococci That Elicits Protective Immunity

2005 ◽  
Vol 73 (3) ◽  
pp. 1671-1683 ◽  
Author(s):  
Ravin Seepersaud ◽  
Sean B. Hanniffy ◽  
Peter Mayne ◽  
Phil Sizer ◽  
Richard Le Page ◽  
...  
Keyword(s):  
Significant Risk ◽  
Invasive Disease ◽  
Invasive Infection ◽  
Dependent Manner ◽  
Leucine Rich Repeat ◽  
Group B Streptococci ◽  
Lethal Challenge ◽  
Life Threatening ◽  
Group B

ABSTRACT Group B streptococci (GBS) usually behave as commensal organisms that asymptomatically colonize the gastrointestinal and urogenital tracts of adults. However, GBS are also pathogens and the leading bacterial cause of life-threatening invasive disease in neonates. While the events leading to transmission and disease in neonates remain unclear, GBS carriage and level of colonization in the mother have been shown to be significant risk factors associated with invasive infection. Surface antigens represent ideal vaccine targets for eliciting antibodies that can act as opsonins and/or inhibit colonization and invasion. Using a genetic screen for exported proteins in GBS, we identified a gene, designated lrrG, that encodes a novel LPXTG anchored surface antigen containing leucine-rich repeat (LRR) motifs found in bacterial invasins and other members of the LRR protein family. Southern blotting showed that lrrG was present in all GBS strains tested, representing the nine serotypes, and revealed the presence of an lrrG homologue in Streptococcus pyogenes. Recombinant LrrG protein was shown in vitro to adhere to epithelial cells in a dose-dependent manner, suggesting that it may function as an adhesion factor in GBS. More importantly, immunization with recombinant LrrG elicited a strong immunoglobulin G response in CBA/ca mice and protected against lethal challenge with virulent GBS. The data presented in this report suggest that this conserved protein is a highly promising candidate antigen for use in a GBS vaccine.

scholarly journals Positive Charges on Lysine Residues of the Extrinsic 18 kDa Protein Are Important to Its Electrostatic Interaction with Spinach Photosystem II Membranes

2005 ◽  
Vol 37 (11) ◽  
pp. 737-742 ◽  
Author(s):  
Jin-Peng Gao ◽  
Zhen-Hua Yong ◽  
Feng Zhang ◽  
Kang-Cheng Ruan ◽  
Chun-He Xu ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Methyl Esters ◽  
Binding Activity ◽  
Water Soluble ◽  
Carboxyl Groups ◽  
Amino Groups ◽  
Charged Amino Acids ◽  
Lysine Residues ◽  
Glycine Methyl Ester ◽  
Positively Charged

Abstract To determine the contribution of charged amino acids to binding with the photosystem II complex (PSII), the amino or carboxyl groups of the extrinsic 18 kDa protein were modified with Nsuccinimidyl propionate (NSP) or glycine methyl ester (GME) in the presence of a water-soluble carbodiimide, respectively. Based on isoelectric point shift, 4–10 and 10–14 amino groups were modified in the presence of 2 and 4 mM NSP, respectively. Similarly, 3–4 carboxyl groups were modified by reaction with 100 mM GME. Neutralization of negatively charged carboxyl groups with GME did not alter the binding activity of the extrinsic 18 kDa protein. However, the NSP-modified 18 kDa protein, in which the positively charged amino groups had been modified to uncharged methyl esters, failed to bind with the PSII membrane in the presence of the extrinsic 23 kDa protein. This defect can not be attributed to structural or conformational alterations imposed by chemical modification, as the fluorescence and circular dichroism spectra among native, GME and NSP-modified extrinsic 18 kDa proteins were similar. Thus, we have concluded that the positive charges of lysyl residues in the extrinsic 18 kDa protein are important for its interaction with PSII membranes in the presence of the extrinsic 23 kDa protein. Furthermore, it was found that the negative charges of carboxyl groups of this protein did not participate in binding with the extrinsic 23 kDa protein associated with PSII membranes.

Susceptibility to Six Antibiotics of Group B Streptococci Isolated from Cerebrospinal Fluid

1985 ◽  
Vol 17 (2) ◽  
pp. 191-193
Author(s):  
Chris Mulder ◽  
Pieter Bol ◽  
Arjan Nabbe ◽  
Bob Zanen
Keyword(s):  
Cerebrospinal Fluid ◽  
Group B Streptococci ◽  
Group B

Tuning of Electronic Properties in Conducting Polymers

2001 ◽  
Vol 66 (8) ◽  
pp. 1208-1218 ◽  
Author(s):  
Guofeng Li ◽  
Mira Josowicz ◽  
Jiří Janata
Keyword(s):  
Hydrogen Bonding ◽  
Binding Site ◽  
Binding Sites ◽  
Polymer Chains ◽  
Electronic Transitions ◽  
Weakly Bound ◽  
Ordered Structures ◽  
Doped Polymer ◽  
Positively Charged ◽  
Repeated Cycling

Structural and electronic transitions in poly(thiophenyleneiminophenylene), usually referred to as poly(phenylenesulfidephenyleneamine) (PPSA) upon electrochemical doping with LiClO4 have been investigated. The unusual electrochemical behavior of PPSA indicates that the dopant anions are bound in two energetically different sites. In the so-called "binding site", the ClO4- anion is Coulombically attracted to the positively charged S or N sites on one chain and simultaneously hydrogen-bonded with the N-H group on a neighboring polymer chain. This strong interaction causes a re-organization of the polymer chains, resulting in the formation of a networked structure linked together by these ClO4- Coulombic/hydrogen bonding "bridges". However, in the "non-binding site", the ClO4- anion is very weakly bound, involves only the electrostatic interaction and can be reversibly exchanged when the doped polymer is reduced. In the repeated cycling, the continuous and alternating influx and expulsion of ClO4- ions serves as a self-organizing process for such networked structures, giving rise to a diminishing number of available "non-binding" sites. The occurrence of these ordered structures has a major impact on the electrochemical activity and the morphology of the doped polymer. Also due to stabilization of the dopant ions, the doped polymer can be kept in a stable and desirable oxidation state, thus both work function and conductivity of the polymer can be electrochemically controlled.

scholarly journals Influence of group B streptococci on piglet pulmonary artery response to bradykinin

1999 ◽  
Vol 86 (1) ◽  
pp. 61-65 ◽  
Author(s):  
Richard M. Whitehurst ◽  
Rachel Laskey ◽  
Ronald N. Goldberg ◽  
Donald Herbert ◽  
Cornelius Van Breemen
Keyword(s):  
Pulmonary Artery ◽  
Contractile Response ◽  
Isometric Force ◽  
Control Group ◽  
Relaxed Controls ◽  
Vascular Response ◽  
Group B Streptococci ◽  
Resting Tension ◽  
Neonatal Group ◽  
Group B

To study whether a sepsis-induced increase in des-Arg9-bradykinin (des-Arg9-BK) and bradykinin (BK) B1-receptor activity participates in the observed increase in pulmonary vascular resistance in neonatal group B streptococcal sepsis (GBS), isometric force bioassays of pulmonary artery (PA) rings were studied, after 4-h exposure to either Krebs or GBS, by using the following protocols: 1) BK dose-response curve, 2) vascular response to BK with N G-nitro-l-arginine methyl ester (l-NAME), and 3) response to des-Arg9-BK (BK metabolite and B1 agonist). PA rings exposed to BK resulted in contraction in the GBS group and a decrease in resting tension in the Control group ( P = 0.034) at a concentration of 10−5 M. GBS-treated PA rings contracted more to des-Arg9-BK than did Controls ( P < 0.001). BK (10−6 M) relaxed preconstricted PA rings incubated in GBS less than BK relaxed Controls ( P < 0.001), and preincubation withl-NAME decreased relaxation in both. These results suggest that GBS decreased endothelium-dependent BK relaxation and increased contractile response to des-Arg9-BK. We speculate that this occurs secondary to upregulation of B1 receptors reflected by B1-agonist-mediated PA contraction.

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