A mutation in yeast mitochondrial DNA results in a precise excision of the terminal intron of the cytochrome b gene

The yeast nuclear gene CBP2 was previously proposed to code for a protein necessary for processing of the terminal intron in the cytochrome b pre-mRNA (McGraw, P., and Tzagoloff, A. (1983) J. Biol. Chem. 258, 9459-9468). In the present study we describe a mitochondrial mutation capable of suppressing the respiratory deficiency of cbp2 mutants. The mitochondrial suppressor mutation has been shown to be the result of a precise excision of the last intervening sequence from the cytochrome b gene. Strains with the altered mitochondrial DNA have normal levels of mature cytochrome b mRNA and of cytochrome b and exhibit wild type growth on glycerol. These results confirm that CBP2 codes for a protein specifically required for splicing of the cytochrome b intron and further suggest that absence of the intervening sequence does not noticeably affect the expression of respiratory function in mitochondria.     

Characterization of the binding activities of proteinase-adhesin complexes from Porphyromonas gingivalis.

Adhesins from oral bacteria perform an important function in colonizing target tissues within the dentogingival cavity. In Porphyromonas gingivalis certain of these adhesion proteins exist as a complex with either of two major proteinases referred to as gingipain R (arginine-specific gingipain) and gingipain K (lysine-specific gingipain) (R. N. Pike, W. T. McGraw, J. Potempa, and J. Travis, J. Biol. Chem. 269:406-411, 1994). With specific proteinase inhibitors, it was shown that hemagglutination by either proteinase-adhesin complex could occur independently of proteinase activity. Significantly, low concentrations of fibrinogen, fibronectin, and laminin inhibited hemagglutination, indicating that adherence to these proteins and not the hemagglutination activity was a primary property of the adhesin activity component of complexes. Binding studies with gingipain K and gingipain R suggest that interaction with fibrinogen is a major function of the adhesin domain, with dissociation constants for binding to fibrinogen being 4 and 8.5 nM, respectively. Specific association with fibronectin and laminin was also found. All bound proteins were degraded by the functional proteinase domain, with gingipain R being more active on laminin and fibronectin and gingipain K being more effective in the digestion of fibrinogen. Cumulatively, these data suggest that gingipain R and gingipain K, acting as proteinase-adhesin complexes, progressively attach to, degrade, and detach from target proteins. Since such complexes appear to be present on the surfaces of both vesicles and membranes of P. gingivalis, they may play an important role in the attachment of this bacterium to host cell surfaces.     

Characterization of binding kinetics of A2AR to Gαs protein by surface plasmon resonance

Because of their surface localization, G protein-coupled receptors (GPCRs) are often pharmaceutical targets as they respond to a variety of extracellular stimuli (e.g., light, hormones, small molecules) that may activate or inhibit a downstream signaling response. The adenosine A_2A receptor (A_2AR) is a well-characterized GPCR that is expressed widely throughout the human body, with over 10 crystal structures determined. Truncation of the A_2AR C-terminus is necessary for crystallization as this portion of the receptor is long and unstructured; however, previous work suggests shortening of the A_2AR C-terminus from 412 to 316 amino acids (A_2AΔ316R) ablates downstream signaling, as measured by cAMP production, to below that of constitutive full-length A_2AR levels. As cAMP production is downstream of the first activation event—coupling of G protein to its receptor—investigating that first step in activation is important in understanding how the truncation effects native GPCR function. Here, using purified receptor and Gα_s proteins, we characterize the association of A_2AR and A_2AΔ316R to Gα_s with and without GDP or GTPγs using surface plasmon resonance (SPR). Gα_s affinity for A_2AR was greatest for apo-Gα_s, moderately affected in the presence of GDP and nearly completely ablated by the addition of GTPγs. Truncation of the A_2AR C-terminus (A_2AΔ316R) decreased the affinity of the unliganded receptor for Gα_s by ～20%, suggesting small changes to binding can greatly impact downstream signaling.     

Diurnal fluctuations in seawater pH influence the response of a calcifying macroalga to ocean acidification

Coastal ecosystems that are characterized by kelp forests encounter daily pH fluctuations, driven by photosynthesis and respiration, which are larger than pH changes owing to ocean acidification (OA) projected for surface ocean waters by 2100. We investigated whether mimicry of biologically mediated diurnal shifts in pH—based for the first time on pH time-series measurements within a kelp forest—would offset or amplify the negative effects of OA on calcifiers. In a 40-day laboratory experiment, the calcifying coralline macroalga, Arthrocardia corymbosa, was exposed to two mean pH treatments (8.05 or 7.65). For each mean, two experimental pH manipulations were applied. In one treatment, pH was held constant. In the second treatment, pH was manipulated around the mean (as a step-function), 0.4 pH units higher during daylight and 0.4 units lower during darkness to approximate diurnal fluctuations in a kelp forest. In all cases, growth rates were lower at a reduced mean pH, and fluctuations in pH acted additively to further reduce growth. Photosynthesis, recruitment and elemental composition did not change with pH, but δ¹³C increased at lower mean pH. Including environmental heterogeneity in experimental design will assist with a more accurate assessment of the responses of calcifiers to OA.     

Risk factors of peripheral arterial disease: a case control study in Sri Lanka

Background

Peripheral artery disease (PAD) is an important global health problem and contributes to notable proportion of morbidity and mortality. This particular manifestation of systemic atherosclerosis is largely under diagnosed and undertreated. For sustainable preventive strategies in a country, it is mandatory to identify country-specific risk factors. We intended to assess the risk factors of PAD among adults aged 40–74 years.

Methods

This case control study was conducted in 2012–2013 in Sri Lanka. Seventy-nine cases and 158 controls in the age group of 40–74 years were selected for the study in order to have case to control ratio 1:2. The criterion for selecting cases and control was based on Ankle brachial pressure index (ABPI). Cases were selected from those who had ABPI 0.85 or less (ABPI ≤0.85) in either lower limb. Controls were selected from those ABPI score between 1.18 and 1.28 in both lower limbs. Only newly identified individuals with PAD were selected as cases. Controls were selected from the same geographical location and within the 5 year age group as cases.

Results

The history of diabetes mellitus more than 10 years (OR 5.8, 95% CI 2.2–14.2), history of dyslipidemia for more than 10 years (OR 4.9, 95% CI 2.1–16.2), history of hypertension for more than 10 years (OR 3.8, 95% CI 1.8–12.7) and smoking (OR 2.9, 95% CI 1.2–6.9), elevated HsCRP (OR 3.7, 95% CI 1.2–12.0) and hyperhomocysteinemia (OR 3.0, 95% CI 1.1–8.1) were revealed as country specific significant risk factor of PAD.

Conclusions

Diabetes mellitus, hypertension, dyslipidemia, smoking as well as elevated homocysteine and HsCRP found as risk factors of PAD. Longer the duration or higher level exposure to these risk factors has increased the risk of PAD. These findings emphasis the need for routine screening of PAD among patients with the identified risk factors.