Plasmodium falciparum: identification and localization of a knob protein antigen expressed by a cDNA clone

Differential screening of cDNA libraries constructed from knobby and predominantly knobless Plasmodium falciparum isolates, identified the sequence SD17. Chromosome blotting experiments have shown that this sequence, which is located on chromosome 2 of most isolates, was deleted in the cloned parasite line E12 of the FCQ27/PNG isolate. Here we show that erythrocytes infected with the SD17-containing cloned line D10 have typical knob structures on their surfaces, whereas those infected with the line E12 lack knobs. An expression clone was constructed from SD17 and used to affinity purify antibodies from the sera of individuals living in areas of Papua New Guinea where malaria is endemic. The antibodies reacted in immunoblotting experiments with a single polypeptide that varied in Mr from 85,000 to 105,000 among different isolates. The antigen was not expressed in the knobless clone E12. Postembedding immunoelectron microscopy showed localization of the antigen over the knobs of FC27 and two other isolates, largely on the cytoplasmic side. We conclude that the parasite antigen corresponding to clone SD17 is a knob protein.     

Structural and catalytic characteristics of Escherichia coli adenylate kinase

The adk gene encoding adenylate kinase in Escherichia coli was cloned in pBR322. Adenylate kinase represented about 4% of total proteins in extracts of cells containing the pBR322:adk plasmid. This allowed preparation of more than 90% pure enzyme in a single-step purification procedure. Amino acid analysis, high performance liquid chromatography separation of trypsin digests, sequence analysis of most peptides, and determination of the N-terminal sequence of the whole protein confirmed the primary structure of E. coli adenylate kinase predicted from the nucleotide sequence of the adk gene (Brune, M., Schumann, R., and Wittinghofer, F. (1985) Nucleic Acids Res. 13, 7139-7151). 2-Nitro-5-thiocyanatobenzoic acid reacted with the single cysteine residue of E. coli adenylate kinase. The cyanylated protein was cleaved upon exposure to alkaline pH, yielding two peptides corresponding to residues 1-76 and 77-214, respectively. A mixture of purified peptides tended to reassociate, recovering both catalytic activity and binding properties for adenine nucleotides. E. coli adenylate kinase has a broader specificity for nucleoside monophosphates than does the mammalian enzyme. In addition to 2'-dAMP, other nucleoside monophosphates such as 3'-dAMP, adenine-9-beta-D-arabinofuranoside 5'-monophosphate, and 7-deazaadenosine (tubercidine) 5'-monophosphate were able to replace AMP as substrate.     

A systematic study of the amino acid compositions and D/L ratios in fossil bones from two french neanderthalian sites

The reaction of racemization in which the L amino acids are reversibly converted into the corresponding D amino acids, proceeds in geological environment at such a slow rate that it may be used as a geochronometer. However, in fossils several parameters may affect the rate of racemization, i.e. moisture, surface, pH buffer and metal cations. This work consists of a systematic study of total amino acid content in fossil bones from two neanderthalian sites. The amino acid distributions of all specimens were determined and compared to that of fresh bone. The D/L amino acid were quantified and expressed in terms of age as a function of the temperature. The results led us to consider the «La Roquette» site older than «Les Canalettes» site.     

Sizing of the Leptospira genome by pulsed-field agarose gel electrophoresis

Pulsed-field gel electrophoresis allowed the determination of the size of the genome of Leptospira, a bacterium of the spirochete family. The three restriction enzymes, NotI (5'GC/GGCCGC), NheI (5'G/CTAGC), ApaI (5'-GGGCC/C) generated DNA fragments of suitable size. The results are compatible with a size of 5000 kb for the chromosome of both the pathogenic and the saprophytic species of Leptospira.     

Nucleotide sequence of the metH gene of Escherichia coli K-12 and comparison with that of Salmonella typhimurium LT2

The Escherichia coli K-12 metH gene, encoding the vitamin B12-dependent homocysteine transmethylase, is located between iclR and lysC in the 91-min region of the chromosome. The metH gene has been sequenced and reveals an open reading frame of 3600 bp encoding a polypeptide of 1200 amino acids (aa) with a calculated Mr of 132 628. The first 414 aa of the deduced polypeptide sequence are 92% identical to the 414 aa deduced from the partially sequenced Salmonella typhimurium LT2 metH gene. In-frame fusions of metH to lacZ were used to confirm the reading frame of the metH gene and to study its regulation. metH was repressed tenfold, presumably indirectly, by L-methionine and the metJ gene product, while vitamin B12 did not induce de novo synthesis of MetH.     

The multicopy appearance of a large inverted duplication and the sequence at the inversion joint suggest a new model for gene amplification.

The amplified DNA of HC50474, a Chinese hamster fibroblast cell line selected in three steps for high resistance to coformycin, consists chiefly of 150 copies of a large inverted duplication including the adenylate deaminase gene. Most if not all of these units are more than 2 x 120 kb long. The inverted duplication was first detected in the cells recovered from the second selection step, at the same chromosomal location as the first step amplified units. Its formation and amplification appear to be coupled since the second step cell line already contained 40 copies of this novel structure. Reamplification of the inverted duplication occurred at the third step of selection concomitant with the loss of amplified DNA acquired during the first step. The head-to-head junction has been formed by recombination within a recombinational hotspot described previously [Hyrien, O., Debatisse, M., Buttin, G. and Robert de Saint Vincent, B. (1987) EMBO J., 6, 2401-2408]. Sequences at the joint and in the corresponding wild-type region reveal that the crossover sites, one of which occurs in the putative promoter region of B2 repeat, are located at the top of significant stem-loop structures and that patchy homologies between the parental molecules on one side of the breakpoints allow alignment of these crossover sites. We present a model which explains the formation and amplification of this and other large inverted duplications by errors in DNA replication.     

Histology of the reproductive tract of hybrids between gonochoristic males and parthenogenetic females of Lepidodactylus lugubris in French Polynesia (Reptilia, Gekkonidae).

Parthenogenetic populations of the gecko Lepidodactylus lugubris are widespread throughout Polynesia. They often occur parapatrically, and occasionally syntopically, with the increasingly rare bisexual populations. In these instances, a small number of hybrid individuals occur and include both "female" and "male" external phenotypes, both with greatly reduced gonads. Histological examination demonstrates that these hybrids possess small ovotestes. The differentiation of the cortical tissue is identical in both "male" and "female" hybrids, but the medullary tissue is more developed in "males." The remainder of the genital tract in "females" resembles that of fertile females in the parthenogenetic and bisexual populations. By contrast, the "male" hybrids are markedly intersexual. In one of the two specimens autopsied, the hemipenes are more or less the same size as those of bisexual males, and the sexual segment of the kidney is hypertrophied and serous. In the other hybrid "male," the hemipenes have a structure similar to that seen in females, and the sexual segment of the kidney is poorly differentiated. In both hybrid "males," the ductus deferens is extremely narrow and further reduced in its middle portion; oviducts are present and resemble those of normal or hybrid females. Thus, embryonic-like gonads are associated with complete and normal female reproductive ducts in hybrid "females." Hybrid "males" also have embryonic-like gonads and feminized genital ducts but associated with secondary sexual characters that match those of sexually active or quiescent normal males.     

Mapping of genes on the linear chromosome of the bacterium Borrelia burgdorferi: Possible locations for its origin of replication

Molecular clones of Borrelia burgdorferi, aetiologic agent of Lyme borreliosis, were isolated and analysed by DNA sequence determination. This procedure yielded B. burgdorferi homologues of gidA, gyrB, gyrA, ftsA and ftsZ. The genes were located on the physical map of the B. burgdorferi linear chromosome. Also mapped were the genes fla and p60 while dnaA was mapped using a heterologous probe. gyrA and gyrB were found to be in tandem and were mapped, along with dnaA at the centre of the chromosome. gidA was located close to the left hand extremity of the chromosome. Because gyrB, dnaA and gidA are normally located within 50 kb of the origin of replication (oriC), we propose two possible sites for oriC in the B. burgdorferi linear chromosome.     

Interneuronal and glial-neuronal gap junctions in the lamina ganglionaris of the compound eye of the housefly,Musca domestics

Summary The cell-body layer of the lamina ganglionaris of the housefly, Musca domestica, contains the perikarya of five types of monopolar interneuron (L1–L5) along with their enveloping neuroglia (Strausfeld 1971). We confirm previous reports (Trujillo-Cenóz 1965; Boschek 1971) that monopolar cell bodies in the lamina form three structural classes: Class I, Class II, and midget monopolar cells. Class-I cells (L1 and L2) have large (8–15 m) often crescentshaped cell bodies, much perinuclear cytoplasm and deep glial invaginations. Class-II cells (L3 and L4) have smaller perikarya (4–8 m) with little perinuclear cytoplasm and no glial invaginations. The midget monopolar cell (L5) resides at the base of the cell-body layer and has a cubshaped cell body. Though embedded within a reticulum of satellite glia, the L1–L4 monopolar perikarya and their immediately proximal neurites frequently appose each other directly. Typical arthropod (-type) gap junctions are routinely observed at these interfaces. These junctions can span up to 0.8 m with an intercellular space of 2–4 nm. The surrounding nonspecialized interspace is 12–20 nm. Freezefracture replicas of monopolar appositions confirm the presence of -type gap junctions, i.e., circular plaques (0.15–0.7 m diam.) of large (10–15 nm) E-face particles. Gap junctions are present between Class I somata and their proximal neurites, between Class I and Class II somata and proximal neurites, and between Class II somata. Intercartridge coupling may exist between such monopolar somata. The cell body and proximal neurite of L5 were not examined. We also find that Class I and Class II somata are extensively linked to their satellite glia via gap junctions. The gap width and nonjunctional interspace between neuron and glia are the same as those found between neurons. The particular arrangement and morphology of lamina monopolar neurons suggest that coupling or low resistance pathways between functionally distinct neurons and between neuron and glia are probably related to the metabolic requirements of the nuclear layer and may play a role in wide field signal averaging and light adaptation.