The structure and evolution of the human salivary proline-rich protein gene family

We present the nucleotide sequences of four members of the six-member human salivary prolinerich protein (PRP) gene family. The four genes are PRB1 and PRB2, which encode basic PRPs, and PRB3 and PRB4, which encode glycosylated PRPs. Each PRB gene is approximately 4.0 kb in length and contains four exons, the third of which is entirely composed of 63-bp tandem repeats and encodes the proline-rich portion of the protein products. Exon 3 contains different numbers of tandem repeats in the different PRB genes. Variation in the numbers of these repeats is also responsible for length variations in different alleles of the PRB genes. We have determined a probable evolutionary history of the human PRP gene family by comparing the nucleotide sequences of the six PRP genes. The present-day six PRP loci probably evolved from a single ancestral gene by four sequential gene duplications, leading to six genes that fall into three subsets, each consisting of two genes. During this evolutionary process, multiple rearrangements and gene conversion occurred mainly in the region from the 3 end of IVS2 and the 3 end of exon 3.     

DIVERGENT AMBULATORY AND GROOMING BEHAVIOR IN SERIALLY BOTTLENECKED LINES OF THE HOUSEFLY

The extent of genome-wide restructuring predicted in bottleneck models of speciation is addressed in assays of non-reproductive behavior in lines of the housefly. After five serial founder-flush cycles of one of three sizes (1, 4, or 16 pairs), each bottleneck line showed significant differentiation from the outbred control in ambulatory levels and grooming sequences in videotaped records of precopulatory activity. Only one line (4-pair) showed overall lethargy which was associated to inbreeding depression in egg-to-adult viability, thus exemplifying a case of probable extinction due to bottlenecks. The two most hyperactive lines (1- and 16-pair) showed very similar directions of differentiation from the control in locomotor activity and grooming behavior, as well as in mating behavior evaluated from a separate study. This high congruence suggested that directional selection toward the phenotypic optima of the ancestor operated on the bottleneck populations and that a 10-fold difference in theoretical inbreeding coefficients did not affect the magnitude of response. The remaining two bottleneck lines showed some independence from these general trajectories, their divergence along minor axes of ancestral intercorrelation structure possibly being more important to the formation of new species. Significant perturbations of the thresholds for execution of grooming and locomotor movements suggested increased evolutionary potential for ritualization (i.e., sexual selection for adoption of non-reproductive behavior into courtship repertoire) due to bottlenecks.     

AN ANALYSIS OF SELECTIONAL RESPONSE IN RELATION TO A POPULATION BOTTLENECK

Selection for increased morphometric shape (ratio of wing length to thorax width) was compared between control (nonbottlenecked) populations and bottlenecked populations founded with two male–female pairs of flies. Contrary to neutral expectation, selectional response was not reduced in bottlenecked populations, and the mean realized heritabilities and additive genetic variances were higher for the bottlenecked lines than for the nonbottlenecked lines. Additive genetic variances based on these realized heritabilities were consistent with independent estimates of genetic variances based on parent–offspring covariances. Joint scaling tests applied to the crosses between selected lines and their controls revealed significant nonadditive components of genetic variance in the ancestor, which were not detected in the crosses involving bottlenecked lines. The nonbottlenecked lines responded principally by changes in one trait or the other (wing length or thorax width) but not in both, and regardless of which trait responded, larger trait size was dominant and epistatic to smaller size. Stabilizing selection for morphometric shape in the ancestor likely molded the genetic architecture to include nonadditive genetic effects.     

Identification of a Novel Stage of Ribosome/Nascent Chain Association with the Endoplasmic Reticulum Membrane

Protein translocation in the mammalian endoplasmic reticulum (ER) occurs cotranslationally and requires the binding of translationally active ribosomes to components of the ER membrane. Three candidate ribosome receptors, p180, p34, and Sec61p, have been identified in binding studies with inactive ribosomes, suggesting that ribosome binding is mediated through a receptor-ligand interaction. To determine if the binding of nascent chain-bearing ribosomes is regulated in a manner similar to inactive ribosomes, we have investigated the ribosome/nascent chain binding event that accompanies targeting. In agreement with previous reports, indicating that Sec61p displays the majority of the ER ribosome binding activity, we observed that Sec61p is shielded from proteolytic digestion by native, bound ribosomes. The binding of active, nascent chain bearing ribosomes to the ER membrane is, however, insensitive to the ribosome occupancy state of Sec61p. To determine if additional, Sec61p independent, stages of the ribosome binding reaction could be identified, ribosome/nascent chain binding was assayed as a function of RM concentration. At limiting RM concentrations, a protease resistant ribosome-membrane junction was formed, yet the nascent chain was salt extractable and cross-linked to Sec61p with low efficiency. At nonlimiting RM concentrations, bound nascent chains were protease and salt resistant and cross-linked to Sec61p with higher efficiency. On the basis of these and other data, we propose that ribosome binding to the ER membrane is a multi-stage process comprised of an initial, Sec61p independent binding event, which precedes association of the ribosome/nascent chain complex with Sec61p.     

Sexual preferences of male hamsters (Mesocricetus auratus) for conspecifics in different endocrine conditions

The behavioral responses of sexually experienced male hamsters toward a pair of anesthetized conspecifics were investigated. Males spent significantly more time licking, sniffing, and mounting neonatally and adult castrated males than intact males. Adult castrated males receiving oil injections were preferred over castrates receiving exogenous testosterone propionate (TP). Ovariectomized females were preferred over intact males, adult castrated males, or spayed females receiving exogenous TP. It was concluded that the absence of an androgen-dependent factor(s) renders an animal more sexually attractive.     

The nature of formate metabolism in greening barley leaves

The metabolism of [³H]formate has been examined in etiolated and greening leaves of barley (Hordeum vulgare), dwarf bean (Phaseolus vulgarls), broad bean (Vicia faba) and corn (Zea mays). Tritium was extensively incorporated by primary leaves incubated for 20-min periods in light or dark. The organic acids and free amino acids were the principal products of formate metabolism but these and other products were more heavily labelled in green tissues. Time course experiments with barley leaves revealed a rapid labelling of serine, accompanied by increasing amounts of ³H in glycine and aspartate as the feeding period was extended. These amino acid products were formed throughout a 4-day greening period with an approximate doubling in total incorporation being due to large accumulations of tritiated glycine and aspartate. The involvement of tetrahydrofolate-dependent reactions in formate metabolism was indicated by inhibition of [¹⁴C] and [³H]formate incorporation by the folate antagonist, aminopterin. Labelling of glycine and serine was also strongly inhibited (up to 90%) when the leaves were incubated with increasing concentrations of isonicotinylhydrazide.     

Calorimetric and chiroptical evidence of aggregate-driven helix formation in carrageenan systems

Thermally induced, order-disorder transitions of iota- and kappa-carrageenan have been monitored by optical rotation and differential-scanning calorimetry in various ionic environments. Conformational ordering in kappa-carrageenan is observed only in the presence of cations that have been shown previously to promote helix-helix aggregation, and shows marked hysteresis between heating and cooling. Iota-carrageenan, by contrast, shows an order-disorder transition in the non-aggregating, tetramethylammonium salt form, at substantially lower temperature than for kappa-carrageenan, and without hysteresis. In the presence of potassium ions, which are known to promote aggregation, iota-carrageenan shows two distinct thermal-transitions, one without hysteresis at the same temperature as observed under non-aggregating conditions, and one with significant hysteresis close to the temperature of the kappa-carrageenan transition. We interpret these transitions as helix-to-coil and aggregated helix-to-coil, respectively. This interpretation is supported by measurements of the enthalpy changes of the transitions; ΔH values show a systematic increase with increasing aggregation and hysteresis. We conclude that the double helix of iota-carrageenan can exist as a stable entity in isolation, but may be further stabilised by aggregation, whereas the kappa-carrageenan helix is stable only when aggregated.     

Prolactin can stimulate general protein synthesis in human breast cancer cells (MCF-7) in long-term culture

Prolactin significantly stimulated protein synthesis rates in a human breast cancer cell line, MCF-7. Total protein per culture also increased to 148% of controls. Proteins precipitated from cell homogenates at pH 4.65 in the presence of calcium ions were resolved by sodium dodecyl sulfate- polyacrylamide gel electrophoresis. The specific radioactivity for almost every polypeptide band increased as a result of protlactin treatment. Cell-type specificity for this prolactin action was indicated by the failure of two other human cell lines (HBL-100 and HEL) to respond similarly. This report is the first demonstration that prolactin has the capability to stimulate general protein synthesis in human breast cancer cells in long-term culture.     

Glycine cleavage and generation of one-carbon units in Euglena gracilis

Euglena gracilis Klebs (strain Z) was maintained in division synchronized autotrophic culture, receiving either air (low CO₂) or 5% CO₂ in     

Associations of like and unlike polysaccharides: Mechanism and specificity in galactomannans,interacting bacterial polysaccharides,and related systems

Chiroptical, rheological, and n.m.r.-relaxation evidence is presented, to identify interactions of two types between different polysaccharides: (1) mutual exclusion of incompatible molecules, with consequent increase in the effective concentration of both; and (2) energetically favourable association of structurally and sterically regular chain-segments. β-1,4-linked plant polysaccharides interact by association of unsubstituted backbone regions, either with like chians, or with sterically compatible, unlike molecules. Extracellular polysaccharides (xanthans) of Xanthomonas plant pathogens maintain their ordered native conformation in solution, and this accounts for their industrially valuable, rheological peculiarities. These materials bind strongly to the plant glycans. Random-coil bacterial gums show no such interactions, although dextran enhances autogelation of galactomannans by exclusion. Extracellular polysaccharides from Arthrobacter species also have ordered native conformations in solution, but do not share the specific interactions of xanthan. Native xanthan shows marked specificity in its interactions with plant glycans, indicating a possible biological role in host-pathogen recognition.