摘要:

The synthesis of a stable substrate for enzymaticNα‐acetylation is described. To this end an analogue of α‐MSH‐(1–10)‐decapeptide with norleucine instead of methionine at position 4 is prepared. t‐Butylation of an intermediate Z‐Tyr‐OMe leads only to about 75% conversion in a few hours' reaction time, and cannot be carried to completion. The [Nle4]‐decapeptide is as good a substrate for enzymaticNα‐acetylation as the original decapeptide

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1982.tb00893.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Tyrosine, tyrosine peptides and derivatives, in total 11 species, were selected as models for the study of optical properties (1Lbband of phenolic group) and side‐chain arrangement (rotamers around Cα– Cβbond) of tyrosine as a function of chemical structure and pH effects. Circular dichroism spectra between 240 and 320 nm and n.m.r. spectra were recorded for the different ionization states. Results are discussed in terms of charge effects fromN‐ andC‐terminal groups and local conformation influence on1Lbband of the phenolic chromophore and on distribution of rotamer populations in side‐chain of tyrosine. Fractions of rotamer populations were estimated from α‐β proton‐proton coupling constants and, in the cases of tyrosine andN‐acetyl‐tyrosine, from15N‐β nitrogen‐proton coupling constants, which allow the stereospecific assignment of the β and β′ protons. The rotamer populations of tyrosine, averaged from all the data of the samples in solution, were then compared with their statistical distribution in the solid state. Interestingly, agreement is excellent when we refer to crystal of tyrosine, tyrosine derivatives or small peptides (31 samples) and poor in the case of proteins. This leads to a discussion on both the validity of using statistical distributions of rotamers in proteins as reference for rotamer preferences inside small peptides in solution and the choice of the appropriate Jgand Jtvalues in Pachler's approach. The possible existence of a correlation between ellipticity and rotamer population

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1982.tb00894.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Human β‐endorphin analogs, [Arg9,19,24,28,29]‐β‐endorphin (I) and [Arg24,28,29]‐β‐endorphin (II), have been synthesized by the solid‐phase method. Peptide II had 86% of the analgesic potency and 216% of the receptor binding activity of the parent molecule. Peptide I had only 18% analgesic potency but its binding activity was more than three time greater than that of hum

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1982.tb00895.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

A conformational analysis of Piv‐l‐Pro‐d‐Pro‐OMe was performed in the solid state using i.r. absorption and X‐ray diffraction. The tertiary amide bond is in thetransconformation, whereas the tertiary peptide bond is in thecisconformation. The sequence of the, ø angles is F, F*. The preferred conformations of the pivaloylamino group, the pyrrolidine rings, and the ester moiety are al

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1982.tb00896.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The complete covalent structure of the insect toxin purified from the venom of the North‐African scorpionAndroctonus australis Hectorwas described. Its amino acid sequence was established by phenylisothiocyanate degradation of several protein derivatives and proteolytic fragments in a liquid protein sequencer using either a “protein” or a “peptide” program. The position of the four disulfide bridges were deduced by analysis of proteolytic peptides before and after performic oxidation, and by partial labeling of the half cystine residues with [14C]‐iodoacetic acid and determining the specific radioactivities of the S‐[14C]‐carboxymethylated phenylthiohydantoin cysteines. The sequences of the insect and mammal toxins from scorpions can be aligned with homology with the positions of seven half‐cystine residues as registers. The mammal and insect toxins have three disulfide bridges at homologous positions. The fourth bridge is different in that Cys12in mammal toxin II is replaced by Cys38in the insect toxin. It is likely that the position of the disulfide bridges is the same for all scorpion neurotoxins active on mammals. We believe that the shift of one half‐cystine residue in the insect toxin may induce a conformational change in the structure of the protein, which, in turn, may partially account for the total specificity of this toxin for in

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1982.tb00897.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Heat‐denaturation of tryptophan synthase α‐subunit fromE. coliand two mutant proteins (Glu 49 ± Gln or Ser; calledGln 49orSer 49, respectively) has been studied by the scanning microcalorimetric method at various pH, in an attempt to elucidate the role of individual amino acid residues in the conformational stability of a protein. The partial specific heat capacity in the native state at 20°, Cp20, has been found to be (0.43 ± 0.02) cal ± K‐1± g‐1, the unfolding heat capacity change, ΔdCp, (0.10 ± 0.01) cal ± K‐1± g‐1, and the unfolding enthalpy value extrapolated to 110°, Δdh110, (9.3 ± 0.5) cal ± g‐1for the three proteins. The value of Cp20was larger than those found for fully compact protein and that of Δdh110was smaller. Unfolding Gibbs energy, ΔdG at 25° forWild‐type, Gln 49, andSer 49were 5.8, 8.4, and 7.1 kcal ± mol‐1at pH 9.3, respectively. Unfolding enthalpy, ΔdH, of the three proteins seemed to be the same and equal to (23.2 ± 1.2) kcal ± mol‐1at 25°. As a consequence of the same value of ΔdH and the different value in ΔdG, substantial differences in unfolding entropy, ΔdS, were found for the three proteins. The values of ΔdG for the three proteins at 25° coincided with those from equilibrium meth

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1982.tb00898.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

In some reptiles, the hemoglobin oxygen affinity is lowered only by CO2and not by the usual phosphate cofactors. To understand the molecular mechanism of this regulation,Caiman crocodylushemoglobin's primary structure has been determined. The alignment of the 141 residues of the α chain as well as the 146 of the β chain were obtained by classical method of sequence analysis and are compared with some mammalian, avian, amphibian, and fish hemoglobin chains. Furthermore, from these sequences, it is possible to explain the non‐interaction of phosphorylated cofactors with the caiman deoxyhemoglobin on the basis of mutations of the amino acids responsible for their fixation on the β chain. Among these residues only lysine β82 is unchanged. In addition a site has been proposed for the fixation of HCO3‐which involves ionic bonds with serine β1 and glutamic acid β144 (Perutzet al.(1981)Nature291, 682

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1982.tb00899.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The conformational and spacial configurations of the biologically active undecapeptide, Substance P, were studied using conformational energy calculations. Low energy conformers of residues 1–5 and 6–11 were found by energy minimization and the two fragments were then combined to find low‐energy structures for Substance P. Several configurational classes were found with different backbone conformations. A comparison of the final low‐energy structures with data from biological tests on analogs of Substance P gives some insight into the conformation required for interaction at the biological r

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1982.tb00900.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Photoreactive derivatives of α‐melanotropin were prepared by selective modification of the single tryptophan residue in position 9 or the amino group of the lysine residue in position 11 by reaction with 2‐nitro‐4‐azidophenylsulfenyl chloride. [2‐Nitro‐4‐azidophenylsulfenyl‐Trp9]‐α‐melanotropin was found to be five times as potent as α‐melanotropin in stimulating lipolysis in isolated rabbit adipocytes. [Nε‐2‐nitro‐4‐azidophenylsulfenyl‐Lys11]‐α‐melanotropin had only 11% of

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1982.tb00901.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

This paper presents the profile map of a protein conformation as a three‐dimensional e‐ø plot, where the third dimension is the residue number. The trajectories of some proteins of known crystalline structure, a few super‐secondary structures in proteins and valinomycin in conformational space are presented and examined. A graphic code for amino acids based on physico‐chemical considerations is devised as part of the present scheme. The representation presented here is useful in correlating primary structure with tertiary fold, intricate sequentially correlated structural features and for the comparison of different conformations of the same or similar

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1982.tb00902.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY