Evaluation of a revised indication for determining adult cochlear implant candidacy.

OBJECTIVE: To evaluate the use of monosyllabic word recognition versus sentence recognition to determine candidacy and long-term benefit for cochlear implantation. STUDY DESIGN: Prospective multi-center single-subject design. METHODS: A total of 21 adults aged 18 years and older with bilateral moderate to profound sensorineural hearing loss and low monosyllabic word scores received unilateral cochlear implantation. The consonant-nucleus-consonant (CNC) word test was the central measure of pre- and postoperative performance. Additional speech understanding tests included the Hearing in Noise Test sentences in quiet and AzBio sentences in +5 dB signal-to-noise ratio (SNR). Quality of life (QoL) was measured using the Abbreviated Profile of Hearing Aid Benefit and Health Utilities Index. RESULTS: Performance on sentence recognition reached the ceiling of the test after only 3 months of implant use. In contrast, none of the participants in this study reached a score of 80% on CNC word recognition, even at the 12-month postoperative test interval. Measures of QoL related to hearing were also significantly improved following implantation. CONCLUSION: Results of this study demonstrate that monosyllabic words are appropriate for determining preoperative candidate and measuring long-term postoperative speech recognition performance. LEVEL OF EVIDENCE: 2c. Laryngoscope, 127:2368-2374, 2017.

bptA (bbe16) is essential for the persistence of the Lyme disease spirochete, Borrelia burgdorferi, in its natural tick vector.

Borrelia burgdorferi (Bb), the agent of Lyme disease, is a zoonotic spirochetal bacterium that depends on arthropod (Ixodes ticks) and mammalian (rodent) hosts for its persistence in nature. The quest to identify borrelial genes responsible for Bb's parasitic dependence on these two diverse hosts has been hampered by limitations in the ability to genetically manipulate virulent strains of Bb. Despite this constraint, we report herein the inactivation and genetic complementation of a linear plasmid-25-encoded gene (bbe16) to assess its role in the virulence, pathogenesis, and survival of Bb during its natural life cycle. bbe16 was found to potentiate the virulence of Bb in the murine model of Lyme borreliosis and was essential for the persistence of Bb in Ixodes scapularis ticks. As such, we have renamed bbe16 a gene encoding borrelial persistence in ticks (bpt)A. Although protease accessibility experiments suggested that BptA as a putative lipoprotein is surface-exposed on the outer membrane of Bb, the molecular mechanism(s) by which BptA promotes Bb persistence within its tick vector remains to be elucidated. BptA also was shown to be highly conserved (>88% similarity and >74% identity at the deduced amino acid levels) in all Bb sensu lato strains tested, suggesting that BptA may be widely used by Lyme borreliosis spirochetes for persistence in nature. Given Bb's absolute dependence on and intimate association with its arthropod and mammalian hosts, BptA should be considered a virulence factor critical for Bb's overall parasitic strategy.

Structural evidence that the 32-kilodalton lipoprotein (Tp32) of Treponema pallidum is an L-methionine-binding protein.

A structure-to-function approach was undertaken to gain insights into the potential function of the 32-kDa membrane lipoprotein (Tp32) of Treponema pallidum, the syphilis bacterium. The crystal structure of rTp32 (determined at a resolution of 1.85 A) shows that the organization of rTp32 is similar to other periplasmic ligand-binding proteins (PLBPs), in that it consists of two alpha/beta domains, linked by two crossovers, with a binding pocket between them. In the pocket, a molecule of L-methionine was detected in the electron density map. Residues from both domains interact with the ligand. One of the crossover regions is comprised of a 3(10)-helix, a feature not typical in other ligand-binding proteins. Sequence comparison shows strong similarity to other hypothetical methionine-binding proteins. Together, the data support the notion that rTp32 is a component of a periplasmic methionine uptake transporter system in T. pallidum.

Conformational changes in a photosensory LOV domain monitored by time-resolved NMR spectroscopy.

Phototropins are light-activated kinases from plants that utilize light-oxygen-voltage (LOV) domains as blue light photosensors. Illumination of these domains leads to the formation of a covalent linkage between the protein and an internally bound flavin chromophore, destabilizing the surrounding protein and displacing an alpha-helix from its surface. Here we use a combination of spectroscopic tools to monitor the kinetic processes that spontaneously occur in the dark as the protein returns to the noncovalent ground state. Using time-resolved two-dimensional (2D) NMR methods, we measured the rate of this process at over 100 independent sites throughout the protein, establishing that regeneration of the dark state occurs cooperatively within a 1.6-fold range of observed rates. These data agree with other spectroscopic measurements of the kinetics of protein/FMN bond cleavage and global conformational changes, consistent with these processes experiencing a common rate-limiting step. Arrhenius analyses of the temperature dependence of these rates suggest that the transition state visited during this regeneration has higher energy than the denatured form of this protein domain despite the fact that there is no global unfolding of the domain during this process.

Structural basis of a phototropin light switch.

Phototropins are light-activated kinases important for plant responses to blue light. Light initiates signaling in these proteins by generating a covalent protein-flavin mononucleotide (FMN) adduct within sensory Per-ARNT-Sim (PAS) domains. We characterized the light-dependent changes of a phototropin PAS domain by solution nuclear magnetic resonance spectroscopy and found that an alpha helix located outside the canonical domain plays a key role in this activation process. Although this helix associates with the PAS core in the dark, photoinduced changes in the domain structure disrupt this interaction. We propose that this mechanism couples light-dependent bond formation to kinase activation and identifies a signaling pathway conserved among PAS domains.