Expression of small heat shock proteins HspB2, HspB8, Hsp20 and cvHsp in different tissues of the perinatal developing pig

Recently, we have described the developmental expression of the small heat shock proteins (sHsps) Hsp27/HspB1 and alphaB-crystallin/HspB5 in different tissues of pigs from almost full-term foetuses to three years old adults (P. Tallot, J. F. Grongnet, J. C. David, Biol. Neonate, 83, 281-288, 2003). The data described in this report extends this study to four other members of the sHsp family (Hsp20/HspB6, cvHsp/HspB7, MKBP/HspB2 and HspB8). We studied expression of these proteins in porcine lens, brain, heart, liver, kidney, lung, skeletal muscle, stomach, and colon, and found a ubiquitous expression of Hsp20 and HspB8 as earlier reported for Hsp27 and alphaB-crystallin. In contrast, cvHsp and HspB2 expression is essentially restricted to heart and muscle. During development, the sHsps tend to (temporarily) increase in stomach, liver, lung, kidney, hippocampus, and striatum, while expression in heart is more or less constant, and a large variation is found in sHsp expression patterns in skeletal muscle. In cerebellum and cortex a temporary decrease of Hsp20 and HspB8 is observed directly after birth. The major impact of this study is that each tissue seems to have a unique profile of sHsp expression, which varies during development and may reflect the need of a particular tissue to maintain at all stages an optimal chaperoning machinery to protect against physiological stress.     

Tsp36, a tapeworm small heat-shock protein with a duplicated alpha-crystallin domain, forms dimers and tetramers with good chaperone-like activity

Small heat shock proteins (sHSPs), which range in monomer size between 12 and 42 kDa, are characterized by a conserved C-terminal alpha-crystallin domain of 80-100 residues. They generally form large homo- or heteromeric complexes, and typically have in vitro chaperone-like activity, keeping unfolding proteins in solution. A special type of sHSP, with a duplicated alpha-crystallin domain, is present in parasitic flatworms (Platyhelminthes). Considering that an alpha-crystallin domain is essential for the oligomerization and chaperone-like properties of sHSPs, we characterized Tsp36 from the tapeworm Taenia saginata. Both wild-type Tsp36 and a mutant (Tsp36C-->R) in which the single cysteine has been replaced by arginine were expressed and purified. Far-UV CD measurements of Tsp36 were in agreement with secondary structure predictions, which indicated alpha-helical structure in the N-terminal region and the expected beta-sandwich structure for the two alpha-crystallin domains. Gel permeation chromatography and nano-ESI-MS showed that wild type Tsp36 forms dimers in a reducing environment, and tetramers in a non-reducing environment. The tetramers are stabilized by disulfide bridges involving a large proportion of the Tsp36 monomers. Tsp36C-->R exclusively occurs as dimers according to gel permeation chromatography, while the nondisulfide bonded fraction of wild type Tsp36 dissociates from tetramers into dimers under nonreducing conditions at increased temperature (43 degrees C). The tetrameric form of Tsp36 has a greater chaperone-like activity than the dimeric form.     

A peptide methionine sulfoxide reductase highly expressed in photosynthetic tissue in Arabidopsis thaliana can protect the chaperone-like activity of a chloroplast-localized small heat shock protein

The oxidation of methionine residues in proteins to methionine sulfoxides occurs frequently and protein repair by reduction of the methionine sulfoxides is mediated by an enzyme, peptide methionine sulfoxide reductase (PMSR, EC 1.8.4.6), universally present in the genomes of all so far sequenced organisms. Recently, five PMSR‐like genes were identified in Arabidopsis thaliana, including one plastidic isoform, chloroplast localised plastidial peptide methionine sulfoxide reductase (pPMSR) that was chloroplast‐localized and highly expressed in actively photosynthesizing tissue ( Sadanandom A et al., 2000 ). However, no endogenous substrate to the pPMSR was identified. Here we report that a set of highly conserved methionine residues in Hsp21, a chloroplast‐localized small heat shock protein, can become sulfoxidized and thereafter reduced back to methionines by this pPMSR. The pPMSR activity was evaluated using recombinantly expressed pPMSR and Hsp21 from Arabidopsis thaliana and a direct detection of methionine sulfoxides in Hsp21 by mass spectrometry. The pPMSR‐catalyzed reduction of Hsp21 methionine sulfoxides occurred on a minute time‐scale, was ultimately DTT‐dependent and led to recovery of Hsp21 conformation and chaperone‐like activity, both of which are lost upon methionine sulfoxidation ( Härndahl et al., 2001 ). These data indicate that one important function of pPMSR may be to prevent inactivation of Hsp21 by methionine sulfoxidation, since small heat shock proteins are crucial for cellular resistance to oxidative stress.     

Metabolic engineering of Lactococcus lactis: the impact of genomics and metabolic modelling

Lactic acid bacteria display a relatively simple and well described metabolism where the sugar source is converted mainly to lactic acid. Here we will shortly describe metabolic engineering strategies that led to the efficient re-routing of the lactococcal pyruvate metabolism to end-products other than lactic acid, including diacetyl and alanine. Moreover, we will review current metabolic engineering approaches that aim at increasing the flux through complex biosynthetic pathways, leading to exopolysaccharides and folic acid. Finally, the (future) impact of the developments in the area of genomics and corresponding high-throughput technologies will be discussed.     

Orofacial clefts and spina bifida: N-acetyltransferase phenotype,maternal smoking,and medication use

BACKGROUND: Orofacial clefts and spina bifida are midline defects with a multifactorial etiology. Maternal smoking and medication use periconceptionally have been studied as risk factors for these malformations. The biotransformation enzyme N-acetyltransferase 2 (NAT2), plays a part in the inactivation of toxic compounds in cigarette smoke and medication. We investigated maternal NAT2 phenotype and the interaction with smoking and medication use periconceptionally on orofacial cleft and spina bifida risk in offspring. METHODS: In this case-control study of 45 mothers of orofacial cleft children, 39 mothers of spina bifida children and 73 control mothers, NAT2 acetylator status was determined by measuring urinary caffeine metabolites. RESULTS: Slow NAT2 acetylators showed no increased risk for orofacial cleft (OR = 1.0, 95% CI: 0.4-2.3) or spina bifida offspring (OR = 0.7, 95% CI: 0.3-1.7) compared to fast NAT2 acetylators. More mothers with orofacial cleft and spina bifida offspring smoked cigarettes (36% and 23% respectively) and used medication periconceptionally (38% and 44% respectively) compared to control mothers (smoking:18%, medication use:19%). No interaction between maternal NAT2 acetylator status and smoking or medication use was observed for orofacial cleft and spina bifida risk. CONCLUSIONS: Maternal smoking and medication use is associated with orofacial cleft risk as well as medication use is with spina bifida. The maternal NAT2 acetylator status, however, was not associated with an increased risk for orofacial cleft or spina bifida offspring, nor in combination with periconceptional smoking or medication use.     

The two homeodomains of the ZmHox2a gene from maize originated as an internal gene duplication and have evolved different target site specificities.

The maize ZmHox2a gene encodes two homeodomains which originated by a 699 bp duplication within an ancestral precursor. The sequences of the two ZmHox2a homeodomains are highly diverged in the N-terminal arm, while residues in the helical part have mostly been conserved. We show here that both ZmHox2a homeodomains are functional DNA-binding motifs but exhibit different target site specificities. CASTing experiments reveal a TCCT motif recognized by HD1 but a GATC tetranucleotide as the recognition sequence of HD2. Mutation of the central nucleotides in both tetranucleotide core motifs abolishes DNA binding. A domain swap experiment indicates that target site specificity is achieved in a combinatorial manner by the contributions of the diverged N-terminal arms together with the slightly different recognition helices. Computer modelling suggests that K47 and H54 in the recognition helices preferentially contact the bases at the 3'-terminus of the tetranucleotide target sequences.     

A standardized method for identifying and counting the vagile and sessile periphyton

Summary A technique adapting the traditional slide method for quantitative study of periphyton populations is described. A substrate of known area and composition (a microscope slide) is exposed to colonization by periphyton in a body of water. At the end of the exposure time the periphyton is fixed while still on the slide and (as suggested by Bodian) impregnated with protargol. This impregnation reveals clearly all the autotrophic and heterotrophic forms in the periphyton population. The entire population is thus permanently preserved for study.Dedicated to Prof. Rolf Danneel on the occasion of his 75th birthday     

Identification of a chitin-binding protein secreted by Pseudomonas aeruginosa

One of the major proteins secreted by Pseudomonas aeruginosa is a 43-kDa protein, which is cleaved by elastase into smaller fragments, including a 30-kDa and a 23-kDa fragment. The N-terminal 23-kDa fragment was previously suggested as corresponding to a staphylolytic protease and was designated LasD (S. Park and D. R. Galloway, Mol. Microbiol. 16:263-270, 1995). However, the sequence of the gene encoding this 43-kDa protein revealed that the N-terminal half of the protein is homologous to the chitin-binding proteins CHB1 of Streptomyces olivaceoviridis and CBP21 of Serratia marcescens and to the cellulose-binding protein p40 of Streptomyces halstedii. Furthermore, a short C-terminal fragment shows homology to a part of chitinase A of Vibrio harveyi. The full-length 43-kDa protein could bind chitin and was thereby protected against the proteolytic activity of elastase, whereas the degradation products did not bind chitin. The purified 43-kDa chitin-binding protein had no staphylolytic activity, and comparison of the enzymatic activities in the extracellular medium of a wild-type strain and a chitin-binding protein-deficient mutant indicated that the 43-kDa protein supports neither chitinolytic nor staphylolytic activity. We conclude that the 43-kDa protein, which was found to be produced by many clinical isolates of P. aeruginosa, is a chitin-binding protein, and we propose to name it CbpD (chitin-binding protein D).     

Role of the lipase-specific foldase of Burkholderia glumae as a steric chaperone

Most lipases of Gram-negative bacteria require a lipase-specific foldase (Lif) in order to fold in the periplasm into their active, protease-resistant conformation prior to their secretion. The periplasmic domain of the Lif (amino acids 44-353) of Burkholderia glumae was purified as a His-tagged protein, and its function in the folding of lipase was studied in vitro. Refolding of the denatured lipase into its active conformation was dependent on the presence of the Lif. Circular dichroism revealed that the lipase refolded in the absence of Lif into a form with a native-like conformation, which was more stable against heat-induced denaturation than the native form, but was enzymatically inactive. This form of the protein could be activated by adding Lif after several hours, which demonstrates that the function of this chaperone is to help lipase to overcome an energetic barrier in the productive folding pathway rather than to prevent it from entering a non-productive pathway. The Lif was shown to interact with the native lipase in protease-protection experiments as well as by affinity chromatography, consistent with a role of the Lif late in the folding process. These results demonstrate that the Lif functions in a way analogous to the propeptides of many bacterial proteases and indicate that the amino acid sequence of the lipase does not contain all the information required for the protein to adopt its three-dimensional structure.