The hydroxypropionaldehyde (HPA) system is a natural defense system synthesized by the probiotic bacterium Lactobacillus reuteri. To elucidate which of the molecules composing the HPA system (3-hydroxypropionaldehyde (3-HPA), reuterin (HPA dimer), and HPA hydrate) is responsible for the potent antimicrobial activity in biological systems, a combination of biochemical, genetic, and proteomic assays was used. The HPA system reacts with sulfhydryl-containing compounds such as cysteine and reduced glutathione (GSH) in solution. In situ, GSH knock-out Escherichia coli is significantly more susceptible to HPA-mediated cell death than E. coli wild type; GSH supplementation protects either bacteria from HPA attack. Proteomic analysis of HPA-treated bacteria ( Haemophilus influenzae ) revealed induction of redox- and heat shock-related proteins. A new antimicrobial mechanism of HPA is proposed, whereby the activity of HPA leads to depletion of free SH- groups in GSH and proteins through the action of 3-hydroxypropionaldehyde, causing an imbalance of the cellular redox status, ultimately resulting in cell death.

BACKGROUND:More than 900 hemoglobin (Hb) variants are currently known. Common techniques used in Hb analysis are electrophoretic and chromatographic assays. In our laboratory, we routinely apply chromatographic methods. To ascertain whether Hb variants are missed with our procedures, we additionally analyzed all samples with mass spectrometry (MS).

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We report a family in which two siblings are compound heterozygotes for Hb S [beta6(A3)GluVal] and a rare beta-globin mutation [IVS-I (-2) (A>C)]. Both patients had significant levels of Hb A, indicating that the IVS-I (-2) mutation is a relatively mild beta(+)-thalassemia (beta(+)-thal) allele. This mutation, in compound heterozygosity with Hb S, does not necessarily lead to a mild clinical course.

Cmb1 (cytosine-mismatch binding 1) is a high-mobility group (HMG) protein of Schizosaccharomyces pombe, which consists of 223 amino acids and has a single HMG domain at the C-terminal end. We have created several mutant and deletion forms of the Cmb1 protein and studied the effects on general DNA binding and specific binding to DNA mismatches and damaged DNA. Cmb1Delta41 (i.e. Cmb1 from which the 41 N-terminal amino acids have been deleted) bound specifically to cytosine-containing mismatches, to the cisplatin-induced intrastrand cross-links cis -GG and cis -AG and to an O (6)-methylguanine lesion. DNA binding was not affected when the 45 N-terminal amino acids were deleted, but was abolished in the absence of the 50 N-terminal amino acids, and was reduced when Cmb1 was truncated by between five and eleven C-terminal amino acids. Cmb1, both with and without the C-terminal truncations, retained its DNA binding affinity after heating at 95 degrees C. The cmb1 gene was induced when S. pombe cells were treated with cisplatin. Mitotic mutation rates were increased in a S. pombe cmb1 null mutant and in a cmb1-(1-212) mutant, which encodes a Cmb1 protein lacking the 11 C-terminal amino acids. We conclude that mutation avoidance by Cmb1 is distinct from Msh2-dependent mismatch repair, but related to nucleotide excision repair.