Bacteriophage T4 head morphogenesis. VII. Terminal stages of head maturation.

Several aspects of the terminal stages of T4 head maturation were investigated using ts and am mutants blocked at single steps of the assembly pathway. We had previously found that cells infected with mutants of gene 13, e.g., tsN38 and amE609, accumulated both stable (10 to 20%)- and fragile (80%)-filled head precursors (Hamilton and Luftig, 1972). Here we showed the following for such gene 13-defective, mutant-infected cells. (i) Using thin-section analysis the pool of phage precursor structures observed under nonpermissive conditions was one-third of that observed when the cells were cultured under permissive conditions. (ii) In order for complete conversion of the precursors into viable phage to occur, there were apparent requirements of metabolic energy, protein, and DNA synthesis. (iii) The intracellular DNA pool under nonpermissive conditions exhibited a 50% distribution between 63S (mature size) and 200 S (concatenate size) DNA, with the latter DNA serving as a precursor pool. Further, this DNA pool when spread onto a protein monolayer exhibited a dispersed array of DNA, strands around a core, which was less dense than that found for the greater than 1,000S DNA concatenate isolated from gene 49-defective infected cells. (iv) When precuations were taken to stabilize the head precursors, such as lysis of the cells into glutaraldehyde, there was a 30% increase in the yield of 1,200S filled heads. Correlating these results and previous results concerning gene 49-defective unfilled heads, we propose that there are several forms of gene 13 fragile head precursors which serve as intermediates between gene 49 unfilled heads and gene 13 stable filled heads. We cannot, however, rule out the possibility that all gene 13-defective heads represent a single class of unstable particles, which decay slowly. In either case, we have shown that gene 13-defective particles are unstable to some degree inside the cell and are highly unstable outside the cell; yet all particles can still be efficiently converted to phage in vivo.     

Properties of condensed bacteriophage T4 DNA isolated from Escherichia coli infected with bacteriophage T4.

Methods developed for isolating bacterial nucleoids were applied to bacteria infected with phage T4. The replicating pool of T4 DNA was isolated as a particle composed of condensed T4 DNA and certain RNA and protein components of the cell. The particles have a narrow sedimentation profile (weight-average s=2,500S) and have, on average, a T4 DNA content similar to that of the infected cell. Their dimensions observed via electron and fluorescence microscopy are similar to the dimensions of the intracellular DNA pool. The DNA packaging density is less than that of the isolated bacterial nucleoid but appears to be roughly similar to its state in vivo. Host-cell proteins and T4-specific proteins bound to the DNA were characterized by electrophoresis on polyacrylamide gels. The major host proteins are the RNA polymerase subunits and two envelope proteins (molecular weights, 36,000 and 31,000). Other major proteins of the host cell were absent or barely detectable. Single-strand breaks can be introduced into the DNA with gamma radiation or DNase without affecting its sedimentation rate. This and other studies of the effects of intercalated ethidium molecules have suggested that the average superhelical density of the condensed DNA is small. However, these studies also indicated that there may be a few domains in the DNA that become positively supercoiled in the presence of high concentrations of ethidium bromide. In contrast to the Escherichia coli nucleoid, the T4 DNA structure remains condensed after the RNA and protein components have been removed (although there may be slight relaxation in the state of condensation under these conditions).     

Survey of aflatoxicosis in farm animals.

Over a 22-month period, 278 submissions of farm animals were made to the North Carolina Diagnostic Laboratory for suspected aflatoxicosis, and 94 cases were confirmed on the basis of finding aflatoxin in the feed and the occurrence of bile ductule proliferation. There was an annual variation in the incidence of aflatoxicosis, as well as a seasonal variation: the peak incidence occurred in the winter, and the minimum incidence occurred during the summer. The annual increase coincided with the corn harvest. All confirmed cases occurred on farms that raised and stored their own corn, and 88% were in swine. The cases were geographically localized in the eastern section of North Carolina (94% of the total cases) where 82% of the swine and 79% of the corn are produced. Mean concentration of aflatoxin in feed samples from the confirmed cases was 3,890 mug/kg, and the mean value for corn used in making the feed was 5,180 mug/kg. Only aflatoxin B1 was found in the samples. These data were interpreted to mean that the incidence and severity of aflatoxicosis is greater than previously suspected, that poor on-farm storage of corn is a primary contributing factor, that aflatoxin formation continues during and after the milling process, and that mycotoxicoses other than aflatoxicosis may cause equal or greater problems.     

Comparative effects of estradiol-17beta and estriol on uterine RNA polymerases I, II, and III in vivo.

The early and later effects of estradiol-17β and estriol on the RNA polymerase activities of uterine nuclei obtained from ovariectomized rats were compared. At 4 hr of hormone action both estradiol-17β and estriol stimulated the activity of polymerase I, but not the activities of polymerases II and III. At 24 hr, however, the effect of estriol had disappeared, whereas estradiol-17β stimulated all three polymerase activities. These results indicate that estrogen-induced growth of the uterus occurs in two phases, initiation and maintenance. Estriol initiates uterine growth, but does not maintain the process. Estradiol-17β, in contrast, does both. The differences in the effects of the two estrogens may reside in their different binding affinities.     

Uptake of alpha-aminoisobutyric acid and phosphate by membrane vesicles derived from growing and quiescent fibroblasts.

Membrane vesicles derived principally from the plasma membrane and endoplasmic reticulum of mouse 3T3 cells transformed by Simian virus 40 take up alpha-aminoisobutyric acid (AIB) and phosphate (Pi). When NaCl is added simultaneously with AIB or Pi, uptake rises two- to three-times above the equilibrium to accumulate AIB or Pi over the control value, in the presence of a Na+ gradient, is almost lost in membrane vesicles derived from benzpyrene-transformed 3T3 cells (BP3T3) arrested in the G1 phase of the cell cycle by serum starvation. When added to the membranes with NaCl and the uptake substrate, a combination of fibroblast growth factor (FGF) and epidermal growth factor EGF restores the ability of the membranes to accumulate AIB and Pi over the control value.     

Calcium-binding protein of bovine intestine. The complete amino acid sequence.

The amino acid sequence for vitamin D-dependent bovine intestinal calcium binding protein has been established. It contains 85 amino acids in a single chain and lacks cysteine, tryptophan, methionine, histidine, and arginine. The NH2-terminal lysine is blocked by an N-acetyl group. Enzymatic digestion with trypsin, chymotrypsin, and pepsin yielded a number of peptides which were purified by two-dimensional high voltage paper electrophoresis. These peptides were examined by end group analysis and sequenced by the dansyl procedure. The absence of tryptophan permitted by a single cleavage of the molecule by N-bromosuccinimide at the tyrosine residue at position 8 and the larger fragment was subjected to automated Edman degradation. By these means, the following sequence was established: N-Ac-Lys-Gln-Ser-Pro-Leu-Glu-Tyr-Ala-Ala-Glu-Lys-Ser-Ile-Gln-Lys-Glu-Ile-Glu-Lys-Gly-Phe-Phe-Lys-Gln-Leu-Leu-Val-Ser-Val-Gln-Lys-Ala-Gly-Asp-Lys-Glu-Ser-Leu-Gln-Pro-Leu-Phe-Thr-Leu-Leu-Lys-Ser-Gly-Pro-Glu-Glu-Asn-Leu-Lys-Glu-Ser-Gln-Asn-Gly-Pro-Asp-Leu-Ls7-Ser-Gly-Pro-Gly-Asn-Asp-Leu-Glu-Glu-Lys-Gly-Thr-Asp-Val-Phe-Ser-Leu-Lys-Gln. Microheterogeneity may exist in the molecule at residue 76 in which position threonine may be replaced by serine. Comparison of the sequence of calcium-binding protein to the "test" sequence of Tufty and Kretsinger ((1975) Science 187, 167-169) proposed to identify E-F hands in muscle proteins suggests that intestinal calcium-binding protein may likewise contain one or possibly two E-F hands which could account for calcium-binding property. Dayhoff alignment scores, however, calculated for calcium-binding protein against nine E-F hands in muscle proteins parvalbumin, troponin and alkali light chains do not indicate that intestinal calcium-binding protein is homologous to these muscle protein chains.     

Purification and regulatory properties of pyruvate kinase from Veillonella parvula.

The nonglycolytic, anaerobic organism Veillonella parvula M4 has been shown to contain an active pyruvate kinase. The enzyme was purified 126-fold and was shown by disc-gel electrophoresis to contain only two faint contaminating bands. The purified enzyme had a pH optimum of 7.0 in the forward direction and exhibited sigmoidal kinetics at varying concentrations o-f phosphoenol pyruvate (PEP), adenosine 5'-monophosphate (AMP), and Mg-2+ ions with S0.5 values of 1.5, 2.0, and 2.4 mM, respectively. Substrate inhibition was observed above 4 m PEP. Hill plots gave slope values (n) of 4.4 (PEP), 2.8 (adenosine 5'-diphosphate), and 2.0 (Mg-2+), indicating a high degree of cooperativity. The enzyme was inhibited non-competitively by adenosine 5'-triphosphate (Ki = 3.4 mM), and this inhibition was only slightly affected by increasing concentration of Mg-2+ ions to 30 mM. Competitive inhibition was observed with 3-phosphoglycerate, malate, and 2,3-diphosphoglycerate but only at higher inhibitor concentrations. The enzyme was activated by glucose-6-phosphate (P), fructose-6-P, fructose-1,6-diphosphate (P2), dihydroxyacetone-P, and AMP; the Hill coefficients were 2.2, 1.8, 1.5, 2.1, and 2.0, respectively. The presence of each these metabolites caused substrate velocity curves to change from sigmoidal to hyperbolic curves, and each was accompanied by an increase in the maximum activity, e.g., AMP greater than fructose-1,6-P2 greater than dihydroxyacetone-P greater than glucose-6-P greater than fructose-6-P. The activation constants for fructose-1,6-P2, AMP, and glucose-6-P were 0.3, 1.1, and 5.3 mM, respectively. The effect of 5 mM fructose-1,6-P2 was significantly different from the other compounds in that this metabolite was inhibitory between 1.2 and 3 mM PEP. Above this concentration, fructose-1,6-P2 activated the enzyme and abolished substrate inhibition by PEP. The enzyme was not affected by glucose, glyceraldehyde-3-P, 2-phosphoglycerate, lactate, malate, fumerate, succinate, and cyclic AMP. The results suggest that the pyruvate kinase from V. parvula M4 plays a central role in the control of gluconeogenesis in this organism by regulating the concentration of PEP.     

Fishing baboons at desert waterholes

Live fish capture by wild chacma baboons is described. Fish were captured from drying desert pools and then covered with sand to immobilize active fish or to facilitate handling. Possible reasons omnivorous primates elsewhere do not capture live fish are considered.