Characterization and primary structures of DNA‐binding HU‐type proteins from Rhizobiaceae

Abstract

The DNA-binding HU-type proteins from several species of Rhizobiaceae including Rhizobium meliloti, two strains of Rhizobium leguminosarum with highly different phenotypic characters and Agrobacterium tumefaciens, were characterized and their amino acid sequences were determined.HU-type proteins isolated from R. leguminosarum L18 and A . tumefaciens are identical and show slight differences with the R. [5] and can fold up circular double-stranded DNA into nucleosomelike structures [6]. This protein, which is associated with the chromosomal and extrachromosomal DNA [7,8], is assumed to be involved in the condensation of the DNA. Furthermore protein HU stimulates the enzymatic replication of the chromosomal origin of E. coli [9] and modulates transcription [l, 101. HU-type proteins have been isolated from a variety of bacterial families [ l l -171 and sequence analyses of these proteins show that they are strongly conserved [18, 191 when compared to other prokaryotic proteins such as cytochromes [20]. Our aim is to investigate the extent of amino acid sequence conservation of HU-type proteins within the family Rhizobiaceae which has been shown to be highly heterogenous [21]. The current classification based upon host infectivity recognizes six species which are distributed into two biochemically very different groups : the slowgrowing Rhizobiaceae and the fast-growing Rhizobiaceae in which the genus Agrobacterium is included because of their close taxonomic relationship. Previous work showed that the physico-chemical properties of the HU-type protein isolated from the slow-growing R. japonicum differ markedly from those of homologous proteins from fast-growing Rhizobiaceae [22]. This paper deals with the comparison of the physicochemical and structural properties of HU-type proteins from fast-growing Rhizobiaceae. On the basis of phenotypic characters, several species, such as Rhizobium meliloti and Agrobacterium, appear homogeneous whereas others are hetAbbreviations. HPLC, high-pressure liquid chromatography; HU, heat-stable protein isolated from Escherichia coli strain U ; PhMeS02F, phenylmethylsulfonyl fluoride; TosPheCH2C1, N-tosylphenylalanyl chloromethane.Enzymes. Carboxypeptidase A (EC 3.4.17.1); trypsin (EC 3.4.21.4).erogeneous [23]. One strain of R. meliloti and Agrobacterium tumefaciens and two strains of R . leguminosarum displaying highly different phenotypic characters were chosen for our study. MATERIALS AND METHODS MaterialsRhizobium meliloti strain 2011 str. 3 (from Institut National de la Recherche Agronomique, Versailles, France), Agrobacterium tumefaciens strain B 6 (from Rijksuniversiteit, Gent, Belgium), Rhizobium leguminosarum strains L18 and LS3 (from Research Institute of Ontario, Canada) were grown as described in [24].Carboxypeptidase A (treated with PhMeS02F) was obtained from Worthington. Acetonitrile for reverse-phase high-pressure liquid chromatography was from Carlo Erba. All solvents and reagents for sequence determination were as indicated in [18]. Nomenclature of proteinsHU-type...

Isolation and characterization of a Streptococcus pyogenes protein that binds to basal laminae of human cardiac muscle

“…The sequence of the first 29 amino acids of the N terminus of GAG-BP revealed no particular secondary structure. The sequence, representing approximately one third of the total protein, has homology with a family of DNA-binding (HU-like) proteins reported in several other genera of bacteria (12,15,16,18,19). The significance of this relationship to the possible role of GAG-BP in poststreptococcal sequalae is not clear at this time because the GAG-BP did not bind to nuclei of myocytes in the tissue sections in immunofluorescence assays nor did purified streptococcal DNA inhibit GAG-BP binding to cardiac muscle in vitro.…”

A HU‐like gene mutation in Rhizobium leguminosarum bv. viciae affects the expression of nodulation genes

“…viciae has been determined to be MNKNELVSAV (Liu et al ., 1998), and is identical to that of the HU‐type protein Hrl18 in R . leguminosarum L18 (Khanaka et al ., 1985). On the basis of this finding, the coding region of R .…”