Frequent duplication and deletion events in the 5S RNA genes and the associated spacer regions of theTriticeae

The 5 S DNA units from 15 grasses in theTriticeae were analysed at the DNA sequence level. Four units carried duplications near the 3-end of the 5 S RNA gene with 3 of the duplications centred on the same base pairs as a duplication previously reported byGerlach & Dyer. The fourth duplication was located 3 downstream from the gene, in the spacer region. Apparent deletions were very frequent when units of the different grasses were compared and it was clear that these deletions did not extend into a 75 bp spacer region upstream from the 5 S RNA gene. This 75 bp region also tended to be more conserved between the grasses as compared to the high level of sequence change in the rest of the spacer region. — Phenetic relationships were established between the grasses using the sequence data. The relationships were generally consistent with the data from other parameters and, in addition, showed that two Australian grasses were closely related to the other Northern hemisphere genera examined. The data concerning the Australian grasses is discussed in relation to the isolated nature of Australia.     

The synthetic precursor specific region of pre-pro-parathyroid hormone forms ion channels in lipid bilayers

We have used the chemically synthesized sequence of pre-pro-parathyroid hormone and several of its analogues to test the notion that the capacity of amphipathic peptides to aggregate in membranes and form ion-permeable channels correlates with their ability to function as signal sequences for secreted proteins. We found that pre-pro-parathyroid hormone (the signal sequence and pro-region of parathyroid hormone (M)), as well as some of its analogues, forms aggregates of monomers which are ion-permeable. The ion-permeable aggregates (2–3 monomers) formed by (M) are voltage-dependent and are more permeable for cations than for anions. The compounds which formed ion channels in bilayers also acted as potential signal sequences. We conclude that the ability of peptides to form ion-permeable pathways in bilayers may be correlated to their ability to function as signal peptides.     

Molecular characterization of the virulence gene virA of the Agrobacterium tumefaciens octopine Ti plasmid

The virulence loci play an essential role in tumor formation by Agrobacterium tumefaciens. Induction of vir gene expression by plant signal molecules is solely dependent on the virulence loci virA and virG. This study focused on the virA locus of the octopine type Ti plasmid pTi15955. The nucleic acid sequence of a 5.7-kilobase fragment encompassing virA was determined. Genetic analysis of this region revealed that virA contains one open reading frame coding for a protein of 91 639 daltons. Immunodetection with antibodies raised against a 35-kDa VirA fusion protein produced in E. coli identified the VirA product in wild-type Agrobacterium cells. Moreover, it is shown that the VirA protein is located in the cytoplasmic membrane fraction of Agrobacterium. These data confirm the proposed regulatory function of VirA whereby VirA acts as a membrane sensor protein to identify plant signal molecules in the environment. The proposed sensory function of VirA strikingly resembles the function of the chemotaxis receptor proteins of E. coli.     

Novel hemoglobin components and their amino acid sequences from the crab-eating macaque (Macaca fascicularis)

Summary We found two types of hemoglobin, T and R, from the crab-eating macaque and compared those to A and Q previously reported. The 22 animals studied showed six different phenotypes, A, R, QA, QT, QAT, and QAR. Analysis of the complete amino acid sequences for the chains of hemoglobins Q, A, T, and R revealed that amino acids at four positions, 8, 55, 71, and 78 from the N-terminal, are variable. In the ^A chain, Thr, Val, Gly, and Gln occupy these positions, and in the ^Q chain the analogous amino acids are Thr, Val, Asp, and Gln, respectively. In the newly found ^T chain they are Thr, Val, Gly, and His; and in the ^R chain, they are Ser, Ile, Gly, and His, respectively. Two amino acids (8 Thr and 79 Gln) in ^A of the crab-eating macaque were found to be different from those in the chain of the Japanese macaque.     

A flexible method to align large numbers of biological sequences

Summary A method for the alignment of two or more biological sequences is described. The method is a direct extension of the method of Taylor (1987) incorporating a consensus sequence approach and allows considerable freedom in the control of the clustering of the sequences. At one extreme this is equivalent to the earlier method (Taylor 1987), whereas at the other, the clustering approaches the binary method of Feng and Doolittle (1987). Such freedom allows the program to be adapted to particular problems, which has the important advantage of resulting in considerable savings in computer time, allowing very large problems to be tackled. Besides a detailed analysis of the alignment of the cytochrome c superfamily, the clustering and alignment of the PIR sequence data bank (3500 sequences approx.) is described.     

Structural Features of Human Monoamine Oxidase A Elucidated from cDNA and Peptide Sequences

Monoamine oxidase (MAO), an important enzyme for the degradation of amine neurotransmitters, has been implicated in neuropsychiatric illness. The amino acid sequence for one form of the enzyme, MAO-A, has been deduced from human cDNA clones and verified against proteolytic peptides. The covalent binding site for the flavin adenine dinucleotide (FAD) cofactor is near the C-terminal region. The presence of features characteristic of the ADP-binding fold suggests that the N-terminal region is also involved in the binding of FAD. These cDNAs should facilitate the study of the structure, function, and intracellular targeting of MAO, as well as the analysis of its expression in normal and pathological states.     

Organization and structure of Volvox beta-tubulin genes

Summary Genomic clones encoding two Volvox -tubulin genes have been isolated and shown to represent the only two -tubulin genes in the genome. Restriction fragment length polymorphism analysis was used to demonstrate that the two genes are genetically linked. One of these genes was sequenced and the mRNA start site(s) determined by primer extension. A comparison of its sequence to those of the two -tubulin genes of Chlamydomonas revealed: (1) a high degree of conservation of the coding region, with the predicted amino acid sequence differing only in the C-terminal residue; (2) extensive sequence conservation in the 5 untranslated leader region and a 16 bp (putative regulatory) sequence in the promoter region; (3) the same number and location of introns, with a short region of homology in intron 1, but little significant homology in introns 2 and 3.