The sequences listed (in single-letter amino acid code) are aligned at the cysteine residue at amino acid 302 by using the numbering system of Ratner et al. (16). The listed sequences have all been published (15,16,22,24,25).Proc. Nati. Acad. Sci. USA Vol. 85, pp. 3198-3202, May 1988
The decapentaplegic (dpp) locus of Drosophila melanogaster is a >55 kb genetic unit required for proper pattern formation during the embryonic and imaginal development of the organism. We have proposed that these morphogenetic functions result from the action of a secreted transforming growth factor-13 (TGF-13)-related protein product encoded by dpp. In this paper we localize 60 mutations on the molecular map of dpp. The positions of these mutations cluster according to phenotypic class, identifying the locations of specific dpp functions. By Northern and cDNA analysis, we characterize five overlapping dpp transcripts. On the basis of the locations of the overlaps relative to a previously sequenced cDNA, it is likely that these transcripts all encode similar or identical polypeptides. We propose that the bulk of dpp DNA consists of extensive arrays of cisregulatory information. The large (>25-kb) 3' c/s-regulatory region represents a novel feature of dpp gene organization.
The transposable element hobo can be mobilized to induce a variety of genetic abnormalities within the germ‐line of Drosophila melanogaster. Strains containing hobos have 3.0 kb elements and numerous smaller derivatives of the element. By analogy with other transposable element systems, it is likely that only the 3.0 kb elements are capable of inducing hobo mobilization. Here, we report that a cloned 3.0 kb hobo, called HFL1, is able to mediate germ‐line transformation and therefore is an autonomous (fully‐functional) transposable element. Germ‐line transformation was observed when HFL1 and a marked hobo element were co‐injected into recipient embryos devoid of endogenous hobos. Integration did not occur in the absence of the 3.0 kb element. A single copy of the marked hobo transposon inserted at each site, and the target sites were widely distributed throughout the genome. Integration occurred at (or very near) the termini of hobo, without internal rearrangement of the hobo or marker gene sequences. The hobo transformation system will allow us to determine the structural and regulatory features of hobo responsible for its mobilization and will provide novel approaches for the molecular and genetic manipulation of the Drosophila genome.
A plasmid carrying the bacteriophage lambda lysis genes under lac control was subjected to hydroxylamine mutagenesis, and mutations eliminating the host lethality of the S gene were selected. DNA sequence analysis revealed 48 single-base mutations which resulted in alterations within the coding sequence of the S gene. Thirty-three different missense alleles were generated. Most of the missense changes clustered in the first two-thirds of the molecule from the N terminus. A simple model for the disposition of the S protein within the inner membrane can be derived from inspection of the primary sequence. In the first 60 residues, there are two distinct stretches of predominantly hydrophobic amino acids, each region having a net neutral charge and extending for at least 20 residues. These regions resemble canonical membrane-spanning domains. In the model, the two domains span the bilayer as a pair of net neutral charge helices, and the N-terminal 10 to 12 residues extend into the periplasm. The mutational pattern is largely consistent with the model. Charge changes within the putative imbedded regions render the protein nonfunctional. Loss of glycine residues at crucial reverse-turn domains which would be required to reorient the molecule to reenter the membrane also inactivate the molecule. Finally, a number of neutral and rather subtle mutations such as Ala to Val and Met to Ile are found, mostly within the putative spanning regions. Although no obvious explanation exists for this subtle and heterogeneous class of mutations, it is noted that all of the changes result in a loss of alpha-helical character as predicted by Chou-Fasman theoretical analysis. Alternative explanations for some of these changes are also possible, including a reduction in net translation rate due to substitution of a rare codon for a common one. The model and the pattern of mutations have implications for the probable oligomerization of the S protein at the time of endolysin release at the end of the vegetative growth period.The bacteriophage lambda has three genes which are directly involved in lysis: S, R, and Rz (16,30,37). The R gene product is a transglycosylase and is responsible for the destruction of the mechanical rigidity of the peptidoglycan (5). The Rz gene product is required for lysis only under conditions which are known to stabilize the outer membrane and may be involved in degradation of the covalent bonds between the outer membrane and the peptidoglycan (37). The S gene encodes a 107-codon polypeptide which is responsible for a lethal event at the cytoplasmic membrane, allowing the release of the R gene product to the periplasm for the degradation of the peptidoglycan (8,14,15). In our hands, only a single polypeptide, with an apparent molecular weight of about 10,000, is elaborated from the wild-type S gene (and not from an Sam mutant allele) in infected cells and in maxicells (3) and is associated with the inner membrane (4). The nature of the event at the cytoplasmic membrane is unclear, but a pleiotropic effect on mem...
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