Lack of an effect of dairy protein (casein) and soy protein on plasma cholesterol of strict vegetarians. An experiment and a critical review

In animals, ingestion of casein, the principal protein in milk, causes hypercholesterolemia, whereas in humans this effect has not been documented. We added 27 g of casein (the amount in 1.1 liters of skim milk and nearly twice the average U.S. intake) for 20 days, and 27 g of soy protein for an additional 20 days to the daily diet of 13 strict vegetarians who consumed no other animal protein during the study period. The protein supplementation increased the ad libitum daily protein intake from 59 g to 82 g. Levels of plasma LDL, HDL, and total cholesterol were not significantly affected by either the casein or the soy supplementation. Over the 40 days of protein supplementation, there were progressive decreases in VLDL cholesterol (VLDL-C) and increases in triglycerides (TG) from pre-study levels, demonstrated by an overall change in the VLDL-C/TG ratio from 0.30 to 0.17 (P = 0.003). Caloric intake and body weight did not change significantly. From the literature on dietary protein and blood lipid levels and from the present data, it appears that neither the amount of protein in the diet nor whether the protein comes from animal or vegetable sources has an important effect on plasma LDL and HDL levels in humans when consumed in physiologic amounts.     

Demonstration of a factor in fraction I of reticulocyte lysates necessary for the steady state accumulation of ubiquitin conjugates of des-75-76-ubiquitin.

Addition of des-75-76-ubiquitin (ubiquitin lacking its two C-terminal glycine residues) to reticulocyte lysates leads to the inhibition of proteolysis and the formation of conjugates between it and native ubiquitin, as demonstrated by the incorporation of both 125I-labeled des-75-76-ubiquitin and 125I-labeled ubiquitin into these conjugates. Conjugate formation is blocked by methylation of the amino groups of des-75-76-ubiquitin, consistent with the concept that the conjugates represent attachment of the ubiquitin alpha-carboxyl group to amino groups of des-75-76-ubiquitin. The lack of significant direct competition for conjugate formation by typical ubiquitinatable proteolysis substrates or by des-73-76-ubiquitin, together with differences in conjugate formation between des-73-76-ubiquitin and des-75-76-ubiquitin demonstrated earlier, indicates that the enzyme involved recognizes the ubiquitin sequence as a substrate for ubiquitination. Increasing concentrations of native ubiquitin first increase and then reduce the steady state level of conjugates of the des-75-76-protein, the inhibitory effects of high concentrations consistent with competition by native ubiquitin for conjugate formation. Upon fractionation of reticulocyte lysates, a factor essential to the net synthesis of conjugates of des-75-76-ubiquitin was demonstrated to be present in Fraction I and to behave as a protein of molecular weight 38,000. The role in this system of a factor from Fraction I other than ubiquitin indicates that a novel pathway is involved.     

Effects of peptide-binding on the proton n.m.r. spectrum of bovine neurophysin-I

The effects of binding L-phenylalanyl-L-phenylalanine amide and related peptides on the 220 MHz and 300 MHz proton n.m.r. spectra of bovine neurophysin-I were studied. Throughout both the aliphatic and aromatic proton regions, marked binding-induced changes in the protein spectrum occur which are best explained by invoking conformational change within the neurophysin dimer, in addition to direct perturbation of individual protein protons by bound peptide. In the region downfield from 6 p.p.m., a new resonance, centered at 6.45 p.p.m. was resolved in 300 MHz spectra. This resonance is tentatively assigned to a non-exchangeable -NH and undergoes a reversible binding-induced broadening. Also in this region, the binding-induced chemical shift change in the ortho ring protons of Tyr-49 was used to explore additional aspects of the kinetics of peptide-binding. The results indicate that peptides with affinities greater than or equal to 10(4) M-1 exhibit slow to intermediate exchange rates on the time scale of the Tyr-49 chemical shift change, but that fast exchange can be achieved with peptides having affinities approximately equal to 10(2) M-1.     

A MULTIPHASIC SCREENING SURVEY IN SAN JOSE

In the interest of economy and of better service to the persons examined, three screening tests of a kind usually made separately were combined and applied in a single examination of 945 employees in four industrial establishments. Miniature x-ray films of the chest were taken, blood specimens drawn and urine samples obtained so that studies and tests might be made to determine the presence of pulmonary or cardiac disease, syphilis, kidney disease, or diabetes. The history of each person examined was taken.Through this multiphasic survey, 13 cases of significant disease previously unknown to the patient were discovered. Sixteen cases of significant disease, previously known, were also disclosed; and in several such cases treatment was begun or resumed.The results in case finding were considerably greater than those of the customary screening for a single disease.     

Binding and spectroscopic properties of ostrich neurophysins. Probing the role of residue 35 at the monomer-monomer interface.

Binding and spectroscopic properties of ostrich neurophysins were examined with emphasis on the behavior of Tyr-35, a residue that provides a potential probe of the monomer-monomer interface and of allosteric interrelationships between this region and the binding site. Mesotocin-associated ostrich neurophysin was found to bind oxytocin and related peptides with affinities comparable to the mammalian proteins, but induced a significantly different optical activity in bound peptides than the mammalian proteins. Gel-filtration studies indicated higher dimerization constants for the ostrich neurophysins than for the bovine neurophysins. Consistent with this, Tyr-35 was found to be largely buried, as monitored by tyrosine titration and lack of reactivity towards tetranitromethane under non-denaturing conditions. Reaction of Tyr-35 of the mesotocin-associated protein with tetranitromethane under denaturing conditions, followed by refolding, allowed isolation of an active product with an altered interface region as partially evidenced by its titration properties and consistent with its markedly altered CD spectrum. Comparison of the CD spectra of the modified and native proteins and analysis of pH effects indicated the contribution of Tyr-35 to an unusual 237 nm band in the mesotocin-associated protein. Small shifts in the 350 nm CD band of nitrated Tyr-35 on binding peptide and apparent effects of nitration on the induced optical activity in bound peptide provided evidence of at least weak structural communication between Tyr-35 and the binding site. However, no significant effect of nitration on binding affinity was observed, suggesting that, in the mesotocin-associated protein, the region around residue 35 is not a stringent modulator of the thermodynamic behavior of the binding site.     

Rab34 GTPase mediates ciliary membrane formation in the intracellular ciliogenesis pathway

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