摘要:

The spin label method has been used to obtain information about conformational changes of histone oligomers taking advantage of the fact that at a low ionic strength and in the presence of other histones about 45% of cysteine residues of histone H3 react with the 3‐maleimido‐2,2,5,5‐tetramethyl‐l‐pyrrolidinyloxyl spin label. For the labeled complexes H3‐H4 and Hn̈ the degree of immobilization of the spin label is a function of the ionic strength. This variation is identical for both complexes within a long range of ionic strengths, including the interval of 0.8‐2 M NaCI, under which conditions interactions are known to exist between the tetramer (H3)2(H4)2and the dimer (H2A) (H2B). This finding suggests a negligible influence of the dimer for modifying the cysteine residue environment of histone H3 on octamer formation. GuHCI treatment at high ionic strength of the labeled complexes gives rise to a non‐lineal increase in the degree of mobility of the spin label. This increase, at low GuHCI concentration (0‐0.5 M GuHCI), is interpreted as showing a lowering in rigidity for the Cys residue environment, without affecting the general stability of the tetramer (H3)2(H4)2. At higher GuHCI concentration (2–3 M GuHCI) the increase in the spin label mobility is related to a dissociation of the complexes in single histones. Our results are consistent with the view that the overall structure of the tetramer, as well as its conformational changes during complex structuration or denaturation, are not strongly affected by the presence of t

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03157.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A normal coordinate treatment was performed on the C7C5conformation using a modified Urey‐Bradley force field refined from previous studies on β‐turns. The predicted frequencies were compared with the experimental ones obtained on the peptide hormone human angiotensin II. The existence of both a β‐turn and a C7C5conformation in solid and in aqueous solution is di

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03158.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The solid phase synthesis of a partially modified retro‐inverso analogue of the bradykinin potentiating peptide BPP9a, [gLys6, (R,S)‐mPhe7, Ala8] BPP9ais described. The analogue, which is activein vitro and in vivo, displays prolonged resistance towards cleavage by angiotensin converting enzyme (A

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03159.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The octameric enolase fromBacillus stearothermophiluswas immobilized onto Sepharose 4B activated by the cyanogen bromide reaction under conditions for achieving essentially a single‐point attachment. The immobilized enzyme was dissociated with guanidine hydrochloride to yield bound monomeric enolase. The Sepharose‐bound subunit regained activity upon removal of the denaturant. It was also possible to rehybridize immobilized monomers to native octamers. Of note, the thermal stability of the immobilized enolase subunit does not appreciably differ from that of the parent soluble octameric enzyme. Thus, these results indicate that single subunits of thermophilic enolase are active and that oligomerization is not a prerequisite for the enzymic activity as well as for thermal stabil

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03160.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Formate salts of amino‐components obtained by acidolysis oftert. butyloxy‐carbonyl‐derivatives with formic acid were converted to the tetrazolate salts which in turn were acylated with active esters. Addition of a tertiary base was not necessary for ready coupling. Further improvement was achieved by using a solution of tetrazole in formic acid for the removal of thetert.butyloxy‐carbony

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03161.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The denaturation of dimeric concanavalin A induced by urea at pH 3 has been studied using optical activity and sedimentation velocity. Under the conditions employed Mn+2and Ca+2are dissociated from the protein, but the basic structural elements are little changed from those prevailing in the functional lectin at pH 5.5 [H.E. Auer and T. Schilz, preceding paper in this issue]. The protein passes through three stages as the urea concentration is varied from 0 to 10 M. Below 4M urea the only effect observed is the loss of optical activity of the aromatic amino acid residues. At 4 M, a conformational change occurs producing extensive aggregation, which persists to 7 M. At 8–10 M urea a disordered monomeric protein molecule prevails. The protein could be reactivated provided that dilution to native conditions was very rapid and the protein concentration remained very low.Kinetics of denaturation were monitored by optical activity at 218, 225 and 283 nm, Transients with one, two or three components were observed, which were resolved by nonlinear regression according to sequential first‐order decay laws. First order character was confirmed by independence of the kinetic parameters from protein concentration over a two‐ to four‐fold range. Enthalpies and entropies of activation for the various steps were also determined. The transients at the three wavelengths monitor changes in β structure, β turns and aromatic groups, respectively. The urea dependence of the rate constants is unique in most cases. It is concluded that different structural elements of the concanavalin A molecule unfold independently from on

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03162.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A predictive method of solubility for protected peptide fragments of globular proteins was described. The solubility prediction was performed on the basis of both the randomness of peptide structures in a solid state and the existence of tertiary peptide bonds such as X‐Pro and X‐(Z)Y bonds, in which X and Y are arbitrary amino acid residues and Z is a suitable protecting group for the X‐Y peptide bond. In order to predict the randomness, the coil conformational parameter, Pe, was utilized. Solubility prediction by this method was success fully applied to the two classes of protected peptides composed solely of hydrophobic and of various amino acid residues. The solubility test results also indicate that the protection of peptide bonds at suitable intervals is effective in achieving a remarkable improvement in the solubility of extraordinarily insoluble peptides. Lastly, the strategy for the selection of the coupling routes in the protein syntheses was pro

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03163.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Boc‐L‐Asu‐L‐Ala‐Gly‐OMe crystallizes in the monoclinic space group P21with cell dimensions a = 14.315(3) Å, b = 9.280(2) Å, c = 14.358(3) Å, β= 103.63 (1) d̀, V= 1853.4(9) Å3, with two molecules in the asymmetric unit. The conformation of the two molecules is characterized by a type II' β‐bend, similar to that predicted earlier by potential energy calculations, stabilized by an intramolecular hydrogen bond. I.r. and1H‐n.m.r. data show that the folded conformation is also stable

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03164.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Inhibition of binding of βh‐endorphin or Leu‐enkephalin by βh‐endorphin analogs of various chain lengths in membrane preparations of the neuroblastoma x glioma NG108–15 cells has been investigated. The removal of even a single residue from theC‐terminus results in the inability of the resulting peptide to completely displace βh‐endorphin. In addition, the proportion of nondisplaceable binding increases with decreasin

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03165.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of changing 1st and 4th amino acid residues on β‐turn preference of tetrapeptide sequences was studied by use of CD spectra of the chromophoric derivatives, which have Dnp‐ and pNA‐groups as the amino and carboxyl substituents, respectively. The effect was examined with the tetrapeptides having such sequences at the 2nd and 3rd positions as ‐L‐Pro‐L‐Asn‐, ‐L‐Pro‐Gly‐, ‐L‐Pro‐D‐Ala‐, ‐L‐Ala‐D‐Leu‐, ‐L‐Ala‐L‐Pro‐, and ‐D‐Ala‐L‐Pro‐. The β‐turn preferences estimated from the CD intensities of the bands due to exciton interaction were found to depend largely on the configurations of the 1st and 4th amino acid residues. When 1st and 2nd (or 3rd and 4th) residues had the same configuration, decreased intensity of the CD band was observed even if the internal sequence had high β‐turn preference. Terminal Gly residues were favorable for

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03166.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY