Vertebrate homeobox genes

In the former part of the review the principal available data aboutHox genes, their molecular organisation and their expression in vertebrate embryos, with particular emphasis for mammals, are briefly summarized.In the latter part we analysed the expression of four mouse homeobox genes related to twoDrosophila genes expressed in the developing head of the fly: Emx1 and Emx2, related toems, and Otx1 and Otx2, related tootd.     

Compositional heterogeneity of the Escherichia coli genome: A role for VSP repair?

E. coli genes that contain a high frequency of the tetranucleotide CTAG are also rich in the tetramers CTTG, CCTA, CCAA, TTGG, TAGG, and CAAG (group-I tetramers). Conversely, E. coli genes lacking CTAG are rich in the tetranucleotides CCTG, CCAG, CTGG, and CAGG (group-II tetramers). These two gene samples differ also in codon usage, amino acid composition, frequency of Dcm sites, and contrast vocabularies. Group-I tetramers have in common that they are depleted by very-short-patch repair (VSP), while group-II tetramers are favored by VSP activity. The VSP system repairs G:T mismatches to G:C, thereby increasing the overall G+C content of the genome; for this reason the CTAG-rich sample has a lower G+C content than the CTAG-poor sample. This compositional heterogeneity can be tentatively explained by a low level of VSP activity on the CTAG-rich sample. A negative correlation is found between the frequency of group-I tetramers and the level of gene expression, as measured by the Codon Adaptation Index (CAI). A possible link between the rate of VSP activity and the level of gene expression is considered.Correspondence to: A. Marine     

Characterization of a new and highly distinguishable HLA-A allele in a Spanish family

Correspondence to: J. L. Vicario.     

Molecular characterization of a fourth isoform of the catalytic subunit of protein phosphatase 2A from Arabidopsis thaliana

We have recently reported the existence of multiple isoforms of the catalytic subunit of protein phosphatase 2A (PP2A) in Arabidopsis thaliana and the molecular cloning of cDNAs encoding three of these proteins (PP2A-1, PP2A-2, PP2A-3). The reported cDNA encoding PP2A-3 was truncated at the 5 terminus, lacking a short fragment of the N-terminal coding sequence. We have now isolated a near full-length cDNA encoding the entire PP2A-3 protein (313 residues). The clone includes 188 nucleotides of 5-untranslated region, where a 44 bp long poly(GA) track is found. We also describe the cloning of a cDNA encoding a fourth isoform of PP2A (PP2A-4). The polypeptide contains 313 residues being 98% identical to PP2A-3 and only 80% identical to both PP2A-1 and PP2A-2. The mRNA for PP2A-4 is 1.4 kb in length and, although predominantly expressed in roots, it is also found in other organs. It is concluded that in A. thaliana the isoforms of PP2A can be grouped in two extremely conserved subfamilies.     

Pigment production from in vitro cultures of Alkanna tinctoria Tausch

Summary An in vitro culture of Alkanna tinctoria Tausch cells was set up in order to investigate the possibility of producing alkannin, a red naphthoquinone naturally present in the root bark of this plant. Furthermore, an in vitro culture of callusderived roots was established and the production of alkannin evaluated. In the different experimental conditions investigated, differences in the production of alkannin derivatives as well as in the type of pigments produced, were observed. The potential use of this technology is discussed.     

Low temperature optical spectroscopy of cobalt-substituted hemocyanin from Carcinus maenas

In this work we report the optical absorption spectra of three cobalt-substituted derivatives of hemocyanin (He) from Carcinus maenas, in the temperature range 300–20 K. The derivatives studied are the mononuclear (Co²⁺)-He with a single cobalt ion in the Cu_A site, the binuclear (Co²⁺)₂-He and the binuclear mixed metal (Co²⁺-Cu¹⁺)-He. At low temperature three main bands are clearly resolved; the temperature dependence of their zeroth, first and second moments sheds light on the stereodynamic properties in the surroundings of the chromophore. Within the limits of the reported analysis, in the binuclear derivatives the motions coupled to the chromophore appear to be essentially harmonic in the whole temperature range investigated; moreover the data are consistent with the presence of an exogenous ligand strongly bound to the two metal ions. For the mononuclear derivative an essentially harmonic behavior is evident only up to 200 K where the data are consistent with the presence of an exogenous ligand much less strongly bound, while at higher temperatures the behavior of the spectra indicates the onset of very large anharmonic contributions to motions, that plausibly involve the above exogenous ligand and, quite likely, the entire active site.Abbreviations He Hemocyanin - M₀ zeroth moment - M₁ first moment - M₂ second moment - (Co^2–)₂-He binuclear bicobalt hemocyanin derivative - (Co²⁺)-He mononuclear monocobalt hemocyanin derivative - (Co²⁺-Cu¹⁺)-He binuclear mixed metals hemocyanin derivative - LFT ligand field theory - CT charge transfer - EPR electronic paramagnetic resonance - XANES X-ray absorption near edge structure Correspondence to: L. Cordone     

Protein dynamics: conformational disorder,vibrational coupling and anharmonicity in deoxy-hemoglobin and myoglobin

In this work we study the temperature dependence of the Soret band lineshape of deoxymyoglobin and deoxyhemoglobin, in the range 300–20 K. To fit the measured spectra we use an approach originally proposed by Champion and coworkers (Srajer et al. 1986; Srajer and Champion 1991). The band profile is modelled as a Voigt function that accounts for the coupling with low frequency vibrational modes, whereas the coupling with high frequency modes is responsible for the vibronic structure of the spectra. Moreover, owing to the position of the iron atom out of the mean heme plane, inhomogeneous broadening brings about a non-Gaussian distribution of 0–0 electronic transition frequencies. The reported analysis enables us to isolate the various contributions to the overall bandwidth, and their temperature dependence points out the relevance of low frequency vibrations and of large scale anharmonic motions starting at temperatures higher than 170 K. Information on the mean iron-heme plane distance and on its temperature dependence, as well as on the heme pocket conformational disorder, is also obtained.Abbreviations Cc Carbon monoxide - Hb Human deoxyhemoglobin A - HbCO human carbonmonoxyhemoglobin A - SWMb spermwhale deoxymyoglobin - SWMbCO spermwhale carbonmonoxymyoglobin - HbO₂ human oxyhemoglobin A - SWMb³⁺-H₂O spermwhale aquometmyoglobin     

Phenylacetaldehyde by acetic acid bacteria oxidation of 2-phenylethanol

Summary This paper reports the production of 2-phenylacetaldehyde from 2-phenylethanol by acetic bacteria. Several strains of acetic bacteria were investigated and three were found to be effective for this bioconversion. Different conditions (different C source for the microorganisms, pH, substrate concentration, cell immobilization) were tested with yields ranging from 30 to 52.6%.