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incubated with 20 ml Sepharose-immobilized monoclonal anti-HA antibodies (Covance). Beads were washed with buffer T without BSA before elution. DSP-induced crosslinks in eluted proteins were thiol-cleaved before separation by 8-16% SDS-PAGE and detection by Sypro Ruby (Bio-Rad). Quinone analysesLipid extractions and quinone detection were performed as described 19 . Hydrogenosomes (5.5 mg protein) were extracted and resuspended in 150 ml 9:1 methanol/ethanol, of which 50 ml was injected onto an HPLC system linked to an ECD. Sequence analysesAccession numbers for sequences used to reconstruct NuoF and NuoE phylogenies are listed in Supplementary Tables 2 and 3. NuoF sequences were aligned with CLUSTALX. NuoE sequences were aligned with Wisconsin Package Version 10.2 programs (Genetics Computer Group). A profile hidden Markov model (HMM) was built from Escherichia coli, Neurospora crassa, Bos taurus, Paracoccus denitrificans and Thermus thermophilus sequences with HMMBUILD. Additional sequences were aligned to the profile with HMMALIGN. Both alignments were edited to remove C-and N-terminal extensions. Analyses of NuoF and NuoE evolution were performed with MRBAYES 30 with the JTT amino-acid substitution model and with two Markov chains Monte Carlo. Chains were run for 100,000 generations, with sampling every 50 generations. The first 5,000 generations were discarded as burn-in. Consensus trees satisfying the more than 50 majority rule were drawn with Treeview, and probabilities of branch partitions were calculated.

The genome of Streptococcus sanguinis is a circular DNA molecule consisting of 2,388,435 bp and is 177 to 590 kb larger than the other 21 streptococcal genomes that have been sequenced. The G؉C content of the S. sanguinis genome is 43.4%, which is considerably higher than the G؉C contents of other streptococci. The genome encodes 2,274 predicted proteins, 61 tRNAs, and four rRNA operons. A 70-kb region encoding pathways for vitamin B 12 biosynthesis and degradation of ethanolamine and propanediol was apparently acquired by horizontal gene transfer. The gene complement suggests new hypotheses for the pathogenesis and virulence of S. sanguinis and differs from the gene complements of other pathogenic and nonpathogenic streptococci. In particular, S. sanguinis possesses a remarkable abundance of putative surface proteins, which may permit it to be a primary colonizer of the oral cavity and agent of streptococcal endocarditis and infection in neutropenic patients.

Mammalian cell invasion assays, using metacyclic trypomastigotes of Trypanosoma cruzi G and CL strains, showed that the CL strain enters target cells in several-fold higher numbers as compared with the G strain. Analysis of expression of surface glycoproteins in metacyclic forms of the two strains by iodination, immunoprecipitation and FACS, revealed that gp90, undetectable in the CL strain, is one of the major surface molecules in the G strain, that expression of gp82 is comparable in both strains and that gp35\50 is expressed at lower levels in the CL strain. Purified gp90 and gp35\50 bound more efficiently than gp82 to cultured HeLa cells. However, the intensity of the Ca# + response triggered in HeLa cells by gp82 was significantly higher than that induced by gp35\50 or gp90. Most of the Ca# + signalling

Aging constitutes the main risk factor for the development of neurodegenerative diseases. This represents a major health issue worldwide that is only expected to escalate due to the ever-increasing life expectancy of the population. Interestingly, axonal degeneration, which occurs at early stages of neurodegenerative disorders (ND) such as Alzheimer's disease, Amyotrophic lateral sclerosis, and Parkinson's disease, also takes place as a consequence of normal aging. Moreover, the alteration of several cellular processes such as proteostasis, response to cellular stress and mitochondrial homeostasis, which have been described to occur in the aging brain, can also contribute to axonal pathology. Compelling evidence indicate that the degeneration of axons precedes clinical symptoms in NDs and occurs before cell body loss, constituting an early event in the pathological process and providing a potential therapeutic target to treat neurodegeneration before neuronal cell death. Although, normal aging and the development of neurodegeneration are two processes that are closely linked, the molecular basis of the switch that triggers the transition from healthy aging to neurodegeneration remains unrevealed. In this review we discuss the potential role of axonal degeneration in this transition and provide a detailed overview of the literature and current advances in the molecular understanding of the cellular changes that occur during aging that promote axonal degeneration and then discuss this in the context of ND.