Recruitment of septin cytoskeletal proteins by botulinum toxin A protease determines its remarkable stability.

Proteolytic cleavage of synaptosomal-associated protein 25 by the light chain of botulinum neurotoxin type A (LCA) results in a blockade of neurotransmitter release that persists for several months in motor neurons. The L428A/L429A mutation in LCA is known to significantly shorten both the proteolytic and neuroparalytic effects of the neurotoxin in mice. To elucidate the cellular mechanism for LCA longevity, we studied the effects of L428A/L429A mutation on the interactome, localization and stability of LCA expressed in cultured neuronal cells.

Metabolomics identifies pyrimidine starvation as the mechanism of 5-aminoimidazole-4-carboxamide-1-β-riboside-induced apoptosis in multiple myeloma cells.

To investigate the mechanism by which 5-aminoimidazole-4-carboxamide-1-β-riboside (AICAr) induces apoptosis in multiple myeloma cells, we conducted an unbiased metabolomics screen. AICAr had selective effects on nucleotide metabolism, resulting in an increase in purine metabolites and a decrease in pyrimidine metabolites. The most striking abnormality was a 26-fold increase in orotate associated with a decrease in uridine monophosphate (UMP) levels, indicating an inhibition of UMP synthetase (UMPS), the last enzyme in the de novo pyrimidine biosynthetic pathway, which produces UMP from orotate and 5-phosphoribosyl-α-pyrophosphate (PRPP).

Defining intact protein primary structures from saliva: a step toward the human proteome project.

Top-down mass spectrometry has been used to investigate structural diversity within some abundant salivary protein families. In this study, we report the identification of two isoforms of protein II-2 which differed in mass by less than 1 Da, the determination of a sequence for protein IB8a that was best satisfied by including a mutation and a covalent modification in the C-terminal part, and the assignment of a sequence of a previously unreported protein of mass 10433 Da. The final characterization of Peptide P-J was achieved, and the discovery of a truncated form of this peptide was reported.

Mass spectral measurements of the apoHDL in horse (Equus caballus) cerebrospinal fluid.

As a continuation of our proteogenomic studies of equine apolipoproteins, we have obtained molecular masses for several of the apolipoproteins associated with the HDL in horse cerebrospinal fluid (CSF). Using electrospray-ionization mass spectrometry (ESI-MS), we report on values for apolipoproteins, A-I and A-II, as well as acylated apoA-I. In comparison with our previously published data on equine plasma apolipoproteins, there appears to be a higher percentage of acylated apoA-I in the CSF than in plasma.

Mass spectrometric measurements of the apolipoproteins of bovine (Bos taurus) HDL.

As is the case in most mammals, high density lipoproteins (HDL) also comprise the major group of lipid carriers that circulate in bovine (Bos taurus) blood. As a continuation of our proteogenomic studies of mammalian apolipoproteins, we have obtained molecular masses for several of the apolipoproteins associated with bovine HDL. The major apolipoprotein on the HDL surface is apoA-I, but other apolipoproteins were also detected.