Co-option of male courtship signals from aggressive display in bowerbirds

The pre-existing trait hypothesis suggests that females evolve a mating preference for an already existing male trait. This hypothesis poses a simple resolution to Darwin's long-standing question of how elaborate, male display traits evolve. The frequently observed convergence of aggressive and courtship displays across a wide array of species provides the only current support for this hypothesis. Here we provide much more detailed supporting evidence from bowerbird skrraa calls used in aggression and courtship. Consistent with the pre-existing trait hypothesis we show that (i) putatively co-opted skrraa calls used in courtship and aggression are homologous, (ii) skrraa calls were used in aggression in bowerbirds before being used in courtship, (iii) historically, intense, aggressive-like courtship calls were present near the time of co-option, and (iv) bower types contemporaneous with co-option emphasize design features that provide females protection from the adverse effects of intense courtship displays. These results, plus evidence for a female preference for males with intense aggressive-like courtship skrraa calls, suggest that aggressive skrraa calls have been co-opted for use in male courtship display     

Modulation of triple-helical stability and subsequent melanoma cellular responses by single-site substitution of fluoroproline derivatives

Collagen is a multifunctional protein, serving as a structural scaffold and a modulator of cellular responses. Prior work has identified distinct regions from several collagen types that promote cell adhesion, spreading, migration, and signal transduction. One of these regions, alpha1(IV)1263-1277 from type IV collagen, mediates these responses via melanoma cell CD44-chondrotin sulfate proteoglycan receptors. In the study presented here, we have used a triple-helical model of alpha1(IV)1263-1277 to evaluate (a) conformational stability and (b) cellular responses based on single-site incorporation of trans-4-fluoro-L-proline (trans-Flp) or cis-4-fluoro-L-proline (cis-Flp) for trans-4-hydroxy-L-proline (trans-Hyp). The structural effects of cis-Flp and trans-Flp substitution were studied by circular dichroism and NMR spectroscopies. The peptide containing a single trans-Flp instead of trans-Hyp was slightly more thermally stable than the parent peptide (T(m) = 37 vs 34 degrees C), while the peptide containing cis-Flp was considerably less stable than the parent peptide (T(m) = 30 degrees C). Melanoma cell adhesion and spreading were examined under conditions where the trans-Hyp-, trans-Flp-, and cis-Flp-containing ligands were approximately 15, <10, and approximately 65% denatured, respectively. Adhesion to each of the three ligands was remarkably sensitive to the respective ligand conformation, with EC(50) values of approximately 2.5, approximately 0.35, and >5.0 microM for the trans-Hyp-, trans-Flp-, and cis-Flp-containing ligands, respectively. Melanoma cell spreading was quantitated over a ligand concentration range of 0.01-50 microM and, in a fashion similar to adhesion, was more extensive on the trans-Flp ligand than on the trans-Hyp ligand. Very low levels of spreading were observed with the cis-Flp-containing ligand at all concentrations tested. Melanoma cell adhesion to and spreading on the three ligands suggested the dramatic biological consequence of even subtle changes in relative triple-helical content. Such subtle changes may model those occurring in the basement membrane during the tumor cell invasion process, and thus provide mechanistic insight into this stage of metastasis.     

Bidirectional gene transfer between Aspergillus fumigatus and Aspergillus nidulans

Abstract The rpmF-plsX-fabH gene cluster of Rhodobacter capsulatus homologous to that of Escherichia coli was identified. rpmF encodes ribosomal protein L32, plsX plays an undefined role in membrane lipid synthesis, and fabH encodes β-ketoacyl-acyl carrier protein synthase III. The R. capsulatus plsX gene complemented a defect in an E. coli strain with the plsX50 mutation. Overproduction of the fabH gene product of R. capsulatus in E. coli resulted in dramatically increased β-ketoacyl-acyl carrier protein synthase III activity. These results indicate that plsX and fabH apparently function the same in R. capsulatus as in E. coli .     

The orlA gene from Aspergillus nidulans encodes a trehalose-6-phosphate phosphatase necessary for normal growth and chitin synthesis at elevated temperatures

A cosmid carrying the orIA gene from Aspergillus nidulans was identified by complementation of an orlA1 mutant strain with DNA from the pKBY2 cosmid library. An orlA1 complementing fragment from the cosmid was sequenced. orlA encodes a predicted polypeptide of 227 amino acids (26 360 Da) that is homologous to a 211-amino-acid domain from the polypeptide encoded by the Saccharomyces cerevisiae TPS2 gene and to almost the entire Escherichia coli of otsB-encoded polypeptide. TPS2 and otsB each specify a trehalose-6-phosphate phosphatase, an enzyme that is necessary for trehalose synthesis. orlA disruptants accumulate trehalose-6-phosphate and have reduced trehalose-6-phosphatate phosphatase levels, indicating that the gene encodes a tre-halose-6-phosphatate phosphatase. Disruptants have a nearly-wild-type morphology at 32°C. When germinated at 42°C, the conidia and hyphae from disruptants are chitin deficient, swell excessively, and lyse. The lysis is almost completely remedied by osmotic stabilizers and is partially remedied by N-acetylglucosamine (GlcNAc). The activity of glutamine:fructose-6-phosphate amido-transferase (GFAT), the first enzyme unique to aminosugar synthesis, is reduced and is labile in orIA disruption strains. The findings are consistent with the hypothesis that trehalose-6-phosphate reduces the temperature stability of GFAT and other enzymes of chitin metabolism at elevated temperatures. The results extend to filamentous organisms the observation that mutations in fungal trehalose synthesis are highly pleiotropic and affect aspects of carbohydrate metabolism that are not directly related to trehalose synthesis.     

Blood in saliva of HIV seropositive drug abusers: possible implication in AIDS transmission.

We have studied hemoglobin concentration in saliva of anti-HIV positive and anti-HIV negative intravenous drug abusers (IVDA) and normal controls and the relationship between hemoglobin concentration in saliva and number of CD4+ cells and clinical status of AIDS in anti-HIV positive IVDA. 120 anti-HIV positive IVDA, 112 anti-HIV negative IVDA and 116 normal healthy subjects not belonging to any risk group for HIV infection completed the study. Saliva was collected at awakening before brushing teeth and the concentration of hemoglobin was determined. Hemoglobin concentration in saliva in basal conditions is higher in anti-HIV positive IVDA with respect to anti-HIV negative IVDA (p less than 0.05) and controls (p less than 0.01). In anti-HIV positive IVDA hemoglobin concentration in saliva is higher in subjects with CD4+ cells less than 200/10(6) l with respect to subjects with CD4+ greater than 200/10(6) l (p less than 0.05) and in subjects with ARC/AIDS with respect to subjects with PGL or who are asymptomatic (p less than 0.01). Subjects with ARC/AIDS have a mean concentration of hemoglobin of 19 micrograms/0.1 ml saliva (range 0-153) which corresponds to 1.3 microliters of blood/ml saliva. If 10 ml of saliva are exchanged during kissing an average of 13 microliters of blood are transferred (110 microliters of whole blood at extreme range). Blood of symptomatic patients has an HIV titer of 7 TCID/microliters which for 10 ml saliva containing an average of 1.3 microliters blood/ml saliva corresponds to an average of 90 TCID (770 TCID at the extreme range).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructural study of the yeast-mycelium transition in Histoplasma capsulatum. II. Changes at 34 degrees C

The ultrastructural changes which occur during the mycelium to yeast transition in Histoplasma capsulatum induced by a temperature shift from 25 degrees C to 34 degrees C are described and compared to those observed after a temperature shift from 25 degrees C to 37 degrees C. 24 hours after the temperature shift to 34 degrees C only 8% of the cells are lysed. However, many mitochondria have lost their characteristic elongated form and have become rounded. Vesicular cristae which are no longer oriented parallel to the long axis of the mitochondria are also observed. In contrast a temperature shift from 25 degrees C to 37 degrees C induces lysis of 70% of the cells; mitochondria are rarely observed in the remaining cells. These ultrastructural changes can be correlated with the uncoupling of oxidative phosphorylation and the production of heat shock proteins.     

Chemical synthesis of proteins

The manipulation of protein structure enables a better understanding of the principles of protein folding, as well as the development of novel therapeutics and drug-delivery vehicles. Chemical synthesis is the most powerful approach for constructing proteins of novel design and structure, allowing for variation of covalent structure without limitations. Here we describe the various chemical methods that are currently used for creating proteins of unique architecture and function.