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Bite infections can contain a mix of anaerobes and aerobes from the patient's skin and the animal's oral cavity, including species of Pasteurella, Streptococcus, Fusobacterium, and Capnocytophaga. Domestic cat and dog bite wounds can produce substantial morbidity and often require specialised care techniques and specific antibiotic therapy. Bite wounds can be complicated by sepsis. Disseminated infections, particularly those caused by Capnocytophaga canimorsus and Pasteurella multocida, can lead to septic shock, meningitis, endocarditis, and other severe sequelae. An emerging syndrome in veterinary and human medicine is meticillin-resistant Staphylococcus aureus (MRSA) infections shared between pets and human handlers, particularly community-acquired MRSA disease involving the USA300 clone. Skin, soft-tissue, and surgical infections are the most common. MRSA-associated infections in pets are typically acquired from their owners and can potentially cycle between pets and their human acquaintances.

ABC transporters represent one of the largest families of membrane proteins that are found in all three phyla of life. Mitochondria comprise up to four ABC systems, ABCB7/ATM1, ABCB10/MDL1, ABCB8 and ABCB6. These half-transporters, which assemble into homodimeric complexes, are involved in a number of key cellular processes, e.g. biogenesis of cytosolic iron-sulfur clusters, heme biosynthesis, iron homeostasis, multidrug resistance, and protection against oxidative stress. Here, we summarize recent advances and emerging themes in our understanding of how these ABC systems in the inner and outer mitochondrial membrane fulfill their functions in important (patho) physiological processes, including neurodegenerative and hematological disorders.

The ATP-binding cassette transporter MDL1 of Saccharomyces cerevisiae has been implicated in mitochondrial quality control, exporting degradation products of misassembled respiratory chain complexes. In the present study, we identified an unusually long leader sequence of 59 amino acids, which targets MDL1 to the inner mitochondrial membrane with its nucleotide-binding domain oriented to the matrix. By contrast, MDL1 lacking this leader sequence is directed into the endoplasmic reticulum membrane with the nucleotide-binding domain facing the cytosol. Remarkably, in both targeting routes, the ATP-binding cassette transporter maintains its intrinsic properties of membrane insertion and assembly, leading to homooligomeric complexes with similar activities in ATP hydrolysis. The physiological consequences of both targeting routes were elucidated in cells lacking the mitochondrial ATP-binding cassette transporter ATM1, which is essential for biogenesis of cytosolic iron-sulfur proteins. The mitochondrial MDL1 complex can complement ATM1 function, whereas the endoplasmic reticulum-targeted version, as well as MDL1 mutants deficient in ATP binding and hydrolysis, cannot overcome the Deltaatm1 growth phenotype.

The ATP-binding cassette half-transporter Mdl1 from Saccharomyces cerevisiae has been proposed to be involved in the quality control of misassembled respiratory chain complexes by exporting degradation products generated by the m-AAA proteases from the matrix. Direct functional or structural data of the transport complex are, however, not known so far. After screening expression in various hosts, Mdl1 was overexpressed 100-fold to 1% of total mitochondrial membrane protein in S. cerevisiae. Based on detergent screens, Mdl1 was solubilized and purified to homogeneity. Mdl1 showed a high binding affinity for MgATP (Kd = 0.26 microm) and an ATPase activity with a Km of 0.86 mm (Hill coefficient of 0.98) and a turnover rate of 2.6 ATP/s. Mutagenesis of the conserved glutamate downstream of the Walker B motif (E599Q) or the conserved histidine of the H-loop (H631A) abolished ATP hydrolysis, whereas ATP binding was not affected. Mdl1 reconstituted into liposomes showed an ATPase activity similar to the solubilized complex. By single particle electron microscopy, a first three-dimensional structure of the mitochondrial ATP-binding cassette transporter was derived at 2.3-nm resolution, revealing a homodimeric complex in an open conformation.

The ABC transporter Mdl1p, a structural and functional homologue of the transporter associated with antigen processing (TAP) plays an important role in intracellular peptide transport from the mitochondrial matrix of Saccharomyces cerevisiae. To characterize the ATP hydrolysis cycle of Mdl1p, the nucleotide-binding domain (NBD) was overexpressed in Escherichia coli and purified to homogeneity. The isolated NBD was active in ATP binding and hydrolysis with a turnover of 25 ATP per minute and a Km of 0.6 mm and did not show cooperativity in ATPase activity. However, the ATPase activity was non-linearly dependent on protein concentration (Hill coefficient of 1.7), indicating that the functional state is a dimer. Dimeric catalytic transition states could be trapped either by incubation with orthovanadate or beryllium fluoride, or by mutagenesis of the NBD. The nucleotide composition of trapped intermediate states was determined using [alpha-32P]ATP and [gamma-32P]ATP. Three different dimeric intermediate states were isolated, containing either two ATPs, one ATP and one ADP, or two ADPs. Based on these experiments, it was shown that: (i) ATP binding to two NBDs induces dimerization, (ii) in all isolated dimeric states, two nucleotides are present, (iii) phosphate can dissociate from the dimer, (iv) both nucleotides are hydrolyzed, and (v) hydrolysis occurs in a sequential mode. Based on these data, we propose a processive-clamp model for the catalytic cycle in which association and dissociation of the NBDs depends on the status of bound nucleotides.

Influenza is an epidemic respiratory illness caused by one of three viral subtypes: A, B, or C. Influenza A causes higher mortality than influenza B and C and is often responsible for pandemics and yearly epidemics of this common, infectious disease. Clinically, patients with influenza present with an abrupt onset of fever, malaise, headache, and a dry, hoarse cough. These symptoms usually last three to five days. Amantadine and rimantadine may be used to prevent and to treat influenza A infection, but not B or C. Ribavirin, however, may be effective treatment for severe influenza pneumonia caused by either A or B subtype, although it is not FDA approved for this application. Annual influenza vaccination should be administered between mid-October and mid-November to any person at increased risk for complications. Health-care workers, those in close contact with high-risk individuals, and personnel vital to community function should also be immunized.

Hantaviruses are a diverse group of RNA arboviruses in the Bunyaviridae family. Although their role as the causative agents of HFRS has been well established, the recent outbreak of a new disease in the Southwest clearly demonstrates the protein clinical manifestations that this pathogen can produce. Furthermore, whereas hantaviruses have been characterized largely as focal agents in the production of geographically delimited diseases, recent trends indicate that endemic areas for the virus are expanding. Outbreaks often occur in clusters as a result of the epizoology of rodent hosts, but isolated cases of hantavirus-related disease also may be observed. Although hantaviruses have proven their pathogenic capability in other areas of the world, it was perceived widely that they were of little consequence to public health in the United States. However, as more is learned about the nature of this truly global infectious agent, its potential danger to mankind becomes increasingly apparent. It is hoped that continued research will elucidate all the facets of hantavirus-induced disease.