Tripartite transporters as mechanotransmitters in periplasmic alternating‐access mechanisms

AbstractTransporters play vital roles in acquiring antimicrobial resistance among pathogenic bacteria. In this study, we report the X-ray structure of NorC, a 14-transmembrane major facilitator superfamily member that is implicated in fluoroquinolone resistance in drug-resistant Staphylococcus aureus strains, at a resolution of 3.6 Å. The NorC structure was determined in complex with a single-domain camelid antibody that interacts at the extracellular face of the transporter and stabilizes it in an outward-open conformation. The complementarity determining regions of the antibody enter and block solvent access to the interior of the vestibule, thereby inhibiting alternating-access. NorC specifically interacts with an organic cation, tetraphenylphosphonium, although it does not demonstrate an ability to transport it. The interaction is compromised in the presence of NorC-antibody complex, consequently establishing a strategy to detect and block NorC and related transporters through the use of single-domain camelid antibodies.

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The FATE Landscape of Sign Language AI Datasets

ACM Transactions on Accessible Computing ◽

10.1145/3436996 ◽

2021 ◽

Vol 14 (2) ◽

pp. 1-45

Author(s):

Danielle Bragg ◽

Naomi Caselli ◽

Julie A. Hochgesang ◽

Matt Huenerfauth ◽

Leah Katz-Hernandez ◽

...

Keyword(s):

Sign Language ◽

New Technology ◽

Individual Data ◽

Community Members ◽

Sign Languages ◽

Language Data ◽

History Of ◽

Language Technologies ◽

And Storage ◽

Access Mechanisms

Sign language datasets are essential to developing many sign language technologies. In particular, datasets are required for training artificial intelligence (AI) and machine learning (ML) systems. Though the idea of using AI/ML for sign languages is not new, technology has now advanced to a point where developing such sign language technologies is becoming increasingly tractable. This critical juncture provides an opportunity to be thoughtful about an array of Fairness, Accountability, Transparency, and Ethics (FATE) considerations. Sign language datasets typically contain recordings of people signing, which is highly personal. The rights and responsibilities of the parties involved in data collection and storage are also complex and involve individual data contributors, data collectors or owners, and data users who may interact through a variety of exchange and access mechanisms. Deaf community members (and signers, more generally) are also central stakeholders in any end applications of sign language data. The centrality of sign language to deaf culture identity, coupled with a history of oppression, makes usage by technologists particularly sensitive. This piece presents many of these issues that characterize working with sign language AI datasets, based on the authors’ experiences living, working, and studying in this space.

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A Poisson Process-Based Random Access Channel for 5G and Beyond Networks

Mathematics ◽

10.3390/math9050508 ◽

2021 ◽

Vol 9 (5) ◽

pp. 508

Author(s):

Alaa Omran Almagrabi ◽

Rashid Ali ◽

Daniyal Alghazzawi ◽

Abdullah AlBarakati ◽

Tahir Khurshaid

Keyword(s):

Poisson Process ◽

Random Access ◽

Communication Technologies ◽

Channel Access ◽

Access Channel ◽

Machine Type Communications ◽

Equal Chance ◽

Random Access Channel ◽

Access Mechanisms

The 5th generation (5G) wireless networks propose to address a variety of usage scenarios, such as enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communications (URLLC). Due to the exponential increase in the user equipment (UE) devices of wireless communication technologies, 5G and beyond networks (B5G) expect to support far higher user density and far lower latency than currently deployed cellular technologies, like long-term evolution-Advanced (LTE-A). However, one of the critical challenges for B5G is finding a clever way for various channel access mechanisms to maintain dense UE deployments. Random access channel (RACH) is a mandatory procedure for the UEs to connect with the evolved node B (eNB). The performance of the RACH directly affects the performance of the entire network. Currently, RACH uses a uniform distribution-based (UD) random access to prevent a possible network collision among multiple UEs attempting to access channel resources. However, in a UD-based channel access, every UE has an equal chance to choose a similar contention preamble close to the expected value, which causes an increase in the collision among the UEs. Therefore, in this paper, we propose a Poisson process-based RACH (2PRACH) alternative to a UD-based RACH. A Poisson process-based distribution, such as exponential distribution, disperses the random preambles between two bounds in a Poisson point method, where random variables occur continuously and independently with a constant parametric rate. In this way, our proposed 2PRACH approach distributes the UEs in a probability distribution of a parametric collection. Simulation results show that the shift of RACH from UD-based channel access to a Poisson process-based distribution enhances the reliability and lowers the network’s latency.

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Principles of Alternating Access in Multidrug and Toxin Extrusion (MATE) Transporters

Journal of Molecular Biology ◽

10.1016/j.jmb.2021.166959 ◽

2021 ◽

pp. 166959

Author(s):

Derek P. Claxton ◽

Kevin L. Jagessar ◽

Hassane S. Mchaourab

Keyword(s):

Alternating Access ◽

Toxin Extrusion

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Resource access mechanisms in networks and SME survival in Ghana

Journal of Enterprising Communities People and Places in the Global Economy ◽

10.1108/jec-08-2017-0072 ◽

2018 ◽

Vol 12 (5) ◽

pp. 611-631 ◽

Cited By ~ 4

Author(s):

George Acheampong ◽

Raphael Odoom ◽

Thomas Anning-Dorson ◽

Patrick Amfo Anim

Keyword(s):

Census Data ◽

Local Level ◽

Directed Network ◽

Resource Access ◽

Content Type ◽

Structural Hole ◽

One Year ◽

Global And Local ◽

Access Mechanisms ◽

Global Influence

Purpose The study aims to determine the resource access mechanism in inter-firm networks that aids SME survival in Ghana. Design/methodology/approach The authors collect census data on a poultry cluster in Ghana and construct a directed network. The network is used to extract direct and indirect ties both incoming and outgoing, as well as estimate the structural holes of the actors. These variables are used to estimate for survival of SMEs after a one-year period using a binary logit model. Findings The study finds that out-indirect ties and structural hole have a significant influence on SME survival. This works through the global influence and the vision advantage that these positions and ties offer the SMEs. Originality/value The study offers SMEs a choice of whom to collaborate with for information (resources) in the form of outgoing and incoming ties at both the global and local level.

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Engineered occluded apo-intermediate of LacY

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1816267115 ◽

2018 ◽

Vol 115 (50) ◽

pp. 12716-12721 ◽

Cited By ~ 1

Author(s):

Irina Smirnova ◽

Vladimir Kasho ◽

H. Ronald Kaback

Keyword(s):

Binding Site ◽

Lactose Permease ◽

Binding Studies ◽

X Ray Crystallography ◽

Sugar Binding ◽

Transport Cycle ◽

Open Structures ◽

Unrestricted Access ◽

Tight Association ◽

Alternating Access

The lactose permease of Escherichia coli (LacY) utilizes an alternating access symport mechanism with multiple conformational intermediates, but only inward (cytoplasmic)- or outward (periplasmic)-open structures have been characterized by X-ray crystallography. It is demonstrated here with sugar-binding studies that cross-linking paired-Cys replacements across the closed cytoplasmic cavity stabilize an occluded conformer with an inaccessible sugar-binding site. In addition, a nanobody (Nb) that stabilizes a periplasmic-open conformer with an easily accessible sugar-binding site in WT LacY fails to cause the cytoplasmic cross-linked mutants to become accessible to galactoside, showing that the periplasmic cavity is closed. These results are consistent with tight association of the periplasmic ends in two pairs of helices containing clusters of small residues in the packing interface between N- and C-terminal six-helix bundles of the symporter. However, after reduction of the disulfide bond, the Nb markedly increases the rate of galactoside binding, indicating unrestricted access to the Nb epitope and the galactoside-binding site from the periplasm. The findings indicate that the cross-linked cytoplasmic double-Cys mutants resemble an occluded apo-intermediate in the transport cycle.

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