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M Salas

Publications and source records attributed to M Salas.

At least 289 records · Page 16Linked to original sources
PubMed1979

Order of assembly of the lower collar and the tail proteins of Bacillus subtilis bacteriophage phi 29.

Extracts obtained after restrictive infection of Bacillus subtilis with mutants in cistron 11 of bacteriophage phi 29 are complemented in vitro by extract donors of the lower collar protein (p11). Purified 11- heads, containing the major capsid protein (p8), the fiber protein (p8.5), the upper collar protein (p10), and the virus DNA, can be also complemented in vitro to produce infective virus. This result suggests that 11- heads are intermediates in phage phi 29 morphogenesis. The order of assembly of the lower collar protein p11 and the tail protein p9 was determined in vitro in two complementation steps. The results obtained indicate that the lower collar protein is assembled before the tail protein.

Bacillus subtilis↗
PubMed1978

Prevention of CeCl3-induced hepatotoxicity by hypolipidemic compounds.

Pretreatment of rats with nafenopin, a hypolipidemic compound, prevents the lethality and hepatotoxicity induced by cerium chloride (CeCl3), a rare earth metal. The increase in hepatic triglycerides and the morphologic changes observed after 48 h of the CeCl3 injection (10 mg/kg) are completely abolished by nafenopin given for 4 days in doses of 250 mg/kg. However, an increase in the frequency of peroxisomes is noted in rats receiving nafenopin and CeCl3, attributable to the hypolipidemic drug pretreatment. In comparing the protective effect of nafenopin with that of CPIB (a structurally related compound) and lentysine (a structurally unrelated agent), it can be seen that nafenopin is about five times more active in decreasing liver triglycerides. The hepatic ultrastructure of rats pretreated with CPIB or lentysine is similar to that of CeCl3-treated controls.

Adenine↗
PubMed1977

Temperature-dependence of stress-induced hepatic autophagy.

In rats, restraint for 48 h elicits hepatic glycogen depletin, autophagy and other ultrastructural changes (e.g. mitochondrial enlargement and rough endoplasmic reticulum disorganization) associated with marked hypothermia. By restoring the body temperature of these animals, all the hepatocytic alterations are abolished.

Adrenal Glands↗
PubMed1977

Assembly of Bacillus subtilis phage phi29. 1. Mutants in the cistrons coding for the structural proteins.

The effect of mutations in the cistrons coding for the phage structural proteins has been studied by analyzing the phage-related structures accumulated after restrictive infection. Infection with susmutants in cistron 8, lacking both the major head and the fiber protein, does not produce any phage-related structure, suggesting a single route for the assembly of phage phi29; infection with ts mutants in this cistron produces isometric particles. Mutants is cistron 9, coding for the tail protein, TP1, produce DNA-free prolate heads with an internal core; these particles are abortive and contain the head proteins HPO, HP1 and HP3, the upper collar protein NP2 and the nonstructural proteins p7, p15 and p16. Mutants in cistron 10, coding for the upper collar protein, NP2, produce DNA-free isometric heads also with an internal core; they contain the head proteins and the nonstructural protein p7, suggesting that this protein forms the internal core. Mutants in cistrons 11 and 12, coding for the lower collar protein, NP3, and the neck appendages, NP1, respectively, give rise to the formation of DNA-containing normal capsids and DNA-free prolate particles, more rounded at the corners than the normal capsids and with an internal core; the DNA-containing 11-particles are formed by the head proteins and the upper collar protein; the DNA-free 11-particles contain, besides these proteins, the nonstructural protein p7 and a small amount of proteins p15 and 16. The DNA-containing 12-particles have all the normal phage structural proteins except the neck appendages, formed by protein NP1; the DNA-free particles are similar to the DNA-free 11-particles. After restricitive infection mutant sus14(1241) has a delayed lysis phenotype and produces a phage burst higher than normal, after artificial lysis. It produces DNA-containing particles, identical to wild-type phage, which have all the normal phage structural proteins, and DNA-free prolate particles, more rounded at the corners than the final phage particles and with an internal core; the last particles contain the same proteins as the DNA-free 11 or 12-particles. These particles could represent a prohead state, ready for DNA encapsulation. None of the DNA-containing particles have the nonstructural proteins p7, p15 or p16, suggesting that these proteins are released from the proheads upon DNA encapsulation.

Bacillus subtilis↗
PubMed1977

Assembly of Bacillus subtilis phage phe29. 2. Mutants in the cistrons coding for the non-structural proteins.

The effect on phage morphogenesis of sus mutations in the cistrons coding for nonstructural proteins has been studied. Mutants in three cistrons analyzed that are involved in phage DNA synthesis, as well as in cistron 16 which codes for a late nonstructural protein, produce prolate capsids which are more rounded at the corners than complete phage heads and have an internal core; they contain the head proteins, the upper collar protein and protein p7, not present in mature phage particles. Mutants in cistron 7 do not produce capsids nor other phage-related structures; this result and the presence of p7 in phage capsids suggest an essential role in capsid assembly for this protein. The protein product of cistron 13 is probably needed for a stable DNA encapsulation since mutants in this cistron produce mainly DNA-free complete phage particles and only about 10% of uninfective DNA-containing complete phage. Cistron 15 codes for a late, partially dispensable, nonstructural protein which is present in the DNA-free capsids produced after infection with the delayed-lysis mutant sus14(1242), used as the wild-type control, or with mutants in cistrons 9, 11,12 and 13. Proteins p15 and p16 are probably involved in the encapsulation of viral DNA in a prohead.

Bacillus subtilis↗
PubMed1977

Order of the two major head protein genes of bacteriophage phi 29 of Bacillus subtilis.

Bacteriophage phi 29 mutation sus8(22) has been mapped by two-factor crosses between markers sus8(769) and ts8(93). Whe sus8(22) infects Bacillus subtilis su- proteins, HP1 (major head protein) and HP3 (fiber protein) are not synthesized; instead, a fragment with a molecular weight of 25,000 is produced. The tryptic peptides of the fragments overlap with corresponding peptides in protein HP1, but not with the peptides of protein HP3, showing that cistron 8 codes for the major head protein HP1.

Bacillus subtilis↗
PubMed1976

Structure and assembly of phage phi29.

Bacteriophage phi29 is a small, morphologically complex, virus with a DNA of molecular mass 12 X 10(6). The most likely structure of the head of phi29 consists of two fivefold symmetric end-caps based on T = 1 icosahedral symmetry, separated by an equatorial row of 5 hexamers. The eighteen genes identified in phi29 genome have been mapped and, in some cases, the gene products have been identified. Five linked genes, four coding for structural proteins (G, A, E, H) and one coding for a non-structural protein (J), are essential to determine the normal shape of the capsid. Protein pJ may be a scaffolding protein. An account of the effects of mutations in phi29 genes is given.

Bacillus subtilis↗
PubMed1976

Synthesis of a class of DNA-binding proteins in synchronized untransformed and virus-transformed cells.

The synthesis of a classs of proteins with affinity for denatured DNA has been studied in synchronized cultures of the established hamster fibroblast line HIL-1 and its virus-transformed derivative NIL-1-hamster sarcoma virus. It has been found that the synthesis of a DNA-binding protein (P6, molecular weight 50 000) in synchronized untransformed NIL-1 cells follows a pattern different from that observed in the transformed cells. The protein is low in stationary cultures of NIL-1 and NIL-1-hamster sarcoma virus but increases after the cells are stimulated to grow, although the time of maximal P6 synthesis relative to cellular DNA synthesis is different in NIL-1 and NIL-1-hamster sarcoma virus. In contrast, the pattern of synthesis of two other DNA-proteins (P7 and P8') in essentially identical in synchronized untransformed and transformed cells. P7 is very low in resting cultures of both types of cells, but greatly increases early after the cells are stimulated to divide, while P8'is hish in stationary cultures and decreases slightly after the initiation of cellular DNA synthesis has occurred.

Cell Division↗
PubMed1976

Bacillus subtilis phage phi29. Characterization of gene products and functions.

A total of 22 phi29-induced proteins have been resolved by slab gel electrophoresis; two of these proteins are the precursor and product fragment, respectively, in the synthesis of the neck appendage protein of the phage. The protein products of 10 out of the 17 cistrons detected in the genome of phage phi29 have been identified. Mutants in two other cistrons fail to synthesize two proteins. Mutants in six genes do not synthesize phage DNA. A cistron, probably involved in the final lysis of the infected bacteria, has been found. Mutants in this gene give place, under restrictive conditions, to delayed lysis and produce, after artificial lysis, a burst size similar or higher than that obtained after wild-type phage infection.

Bacillus subtilis↗
PubMed1976

Isolation of a strong suppressor of nonsense mutations in Bacillus subtilis.

By treatment of Bacillus subtilis MO-101-P spoA- met thr- su- with ethyl methanesulfonate, a strong suppressor strain of nonsense mutations, B. subtilis MO-101-P spoA- [met-]+thr- su+44, was isolated. This strain does not suppress phage phi 29 mutant susB47, selected on a B. subtilis strain containing the su+3 suppressor isolated by Georgopoulos. A revertant from this mutant, susB610, was isolated, being suppressed by both the su+3 and su+44 suppressor strains. The efficiency of suppression by strain su+44 is about 50%. The experiments shown in this paper suggest that strain su+44 contains an amber and strain su+3 an ochre suppressor.

Bacillus subtilis↗
PubMed1976

Prevention by steroids of cerium hepatotoxicity.

In female rats, the lethality and hepatotoxicity of cerous chloride (CeCl3) were significantly altered by pretreatment with steroidal and nonsteroidal compounds (pregnenolone-16alpha-carbonitrile "PCN", dexamethasone, spironolactone, phenobarbital) that stimulate hepatic drug-metabolizine enzyme activity and by estradiol. PCN, estradiol, and dexamethasone considerably decreased hepatic triglycerides, but the latter steroid also greatly sensitized the animals to CeCl3 lethality. Spironolactone and phenobarbital similarly lowered the triglyceride level but not significantly. Light and electron microscopy indicated that the hepatocytic damage elicited by CeCl3 was decreased significantly by PCN, estradiol, and dexamethasone. The steroids may have altered the distribution and binding of the metal to the endoplasmic reticulum (er) thus protecting these membranes against the effect of cerium.

Animals↗