摘要:

Symmetrical features were observed in the amino acid sequences of some biologically active peptides. It is suggested that this approximate symmetry is reflected in the conformations of the peptides at their respective biological receptors, and has arisen by natural selection as both peptides and receptors evolved to optimise their mutual fit. It follows that the binding site for each peptide at its receptor would share the same symmetry element. This would arise if the peptide binds to two symmetrically related similar or identical submits in the receptor.

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03476.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Tosyl‐triethylenetetramine‐Sepharose (Tos‐T*‐Sepharose) and carbobenzoxy‐triethylenetetramine‐Sepharose (Z‐T‐Sepharose) were found to be adsorbents utilizable in the purification of several microbial and animal proteases. The former Sepharose derivative adsorbed α‐chymotrypsin, trypsin, subtilisin, thermolysin and neutral subtilopeptidase at neutral pH range, and acid proteases such as pepsin and Rhizopus niveus protease at pH 3.5–6.5. α‐Chymotrypsin and trypsin were eluted with 0.1 N acetic acid and Rhizopus protease with 0.5 N acetic acid, thermolysin with 1 M guanidine ˙ HCI or 33% ethyleneglycol, whilst pepsin was recovered by elution with 2 M guanidine ˙ HCl at pH 3.5. The binding of neutral subtilopeptidase and subtilisin to this adsorbent was comparatively weak and both the enzymes were recovered by elution with 0.5 I M Nacl at neutral pH. On the other hand, Z‐T‐Sepharose was found to bind tightly to these proteolytic enzymes except neutral subtilopeptidase. Trypsin and α‐chymotrypsin were released from the adsorbent column with 1 M p‐toluenesulfonate, and subtilisin with 1 M guanidine ˙ HCl or 33% ethyleneglycol at neutral pH region. By these chromatographic procedures, the specific activities of these proteolytic enzymes increased effectively. Comparison of the binding abilities of acetyl‐, benzoyl‐, tosyl‐ and carbobenzoxy‐T‐Sepharoses to these enzymes suggests that hydrophobicity of tosyl and carbobenzoxy groups plays an impor

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03477.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The reaction of the amino groups of bovine serum albumin (BSA) with diacetyl‐cycloserine (I) at pH 7.2–9.0 proceeded with both acylation by the diacetyl‐β‐aminooxy‐D‐alanyl (DAA) group and acetylation. The number of DAA groups was determined by their conversion to cycloserine (III) which can be accurately measured in micromolar amounts. The method was developed using the model compound diacetyl‐β‐aminooxy‐D‐alanine butyl amide (II) which was converted to β‐aminooxy‐D‐alanine butyl amide (IV) by methanolysis and then to cycloserine by basic ring‐closure of IV. Calculations using results obtained by this method combined with the experimentally determined number of free amino groups in the modified BSA indicated that the reaction of excess I with BSA effected the acetylation of about 35 and the acylation with DAA groups of about 22 of the 59 amino groups. These findings were supported by experiments demonstrating that the amount of acetic acid formed by hydrolysis of the modified BSA was approximately that predicted from the resul

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03478.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

8‐L‐Homoarginine‐vasotocin and its I‐deamino derivative were synthesized by the solid phase method. Both compounds possessed high activities in the uterus contraction and fowl depressor assays and showed higher pressor activities than the corresponding vasopressins. Homoarginine‐vasotocin, unexpectedly, was a more potent antidiuretic agent than its deamino

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03479.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Single crystals of the plasma protein ceruloplasmin (CP) and its two modified forms: neuraminidase‐treated CP (asialoCP) and NaN3‐inhibited CP (NaN3‐CP) suitable for X‐ray studies have been grown. The native CP crystallizes as described previously by Magdoff‐Fairchield et al. (1969) in the tetragonal space group 14 (a = b = 268.2 Å, c = 129.1 å) with two protein molecules in the asymmetric part of a unit cell. AsialoCP crystals belong to the trigonal space group P 3121 or P321 (a = b = 215.0 å, c = 84.5 å) and have one protein molecule in the asymmetric part of a unit cell. NaN3‐CP crystals are isomorphous to crystals of native CP. Despite some differences in electrophoretic mobility and optical properties, the conformations of the native CP molecule and its modified forms are similar, as can be concluded from a study of ORD

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03480.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Two new ACTH‐analogues, an octadecapeptide amide and a tetracosapeptide containing the lower homologue of arginine (norarginine) in position 8, have been synthesized by the generally accepted method. Special attention was paid to the synthesis of the required tetrapeptide representing the 7–10 sequence, which was obtained either by direct introduction of L‐nitronorarginine or by amidination of the γ‐amino function in a protected peptide containing α, γ‐diaminobutyric acid.Biological activity determination showed that the shortening of the arginine side chain in position 8 results in the formation of active AC

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03481.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Two analogues of α‐MSH are described, in which the tryptophan residue occuring in position 9 of the natural hormone has been replaced by pentamethyl‐phenylalanine and phenylalanine, respectively. The analogues were synthesized via a conventional procedure and the [Phe9]‐analogue also by a semi‐synthetic approach, which demonstrated thefavourable properties of the applied, new amino‐protecting Msc function for this purpose.The widely different electron donor properties of the substituted residues were accompanied by a large difference in melanocyte stimulating activity of the analogues. The [Pmp9]‐analogue, having donor properties comparable to those of the natural compound, was four to five times more active than the analogue containing the poorly donating Phe residue. The opposite effect was noted in in vivo lipolysi

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03482.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The effect of modification of carboxyl groups of Ribonuclease‐Aaon the enzymatic activity and the antigenic structure of the protein has been studied. Modification of four of the eleven free carboxyl groups of the protein by esterification in anhydrous methanol/0.1 M hydrochloric acid resulted in nearly 80% loss in enzymatic activity but had very little influence on the antigenic structure of the protein. Further increases in the modification of the carboxyl groups caused a progressive loss in immunological activity, and the fully methylated RNase‐A exhibited nearly 30% immunological activity. Concomitant with this change in the antigenic structure of the protein, the ability of the molecule to complement with RNase‐S‐protein increased, clearly indicating the unfolding of the peptide “tail” from the remainder of the molecule. The susceptibility to proteolysis, accessibility of methionine residues for orthobenzoquinone reaction and the loss in immunological activity of the more extensively esterified derivatives of RNase‐A are suggestive of the more flexible conformation of these derivatives as compared with the compact native conformation. The fact that even the fully methylated RNase‐A retains nearly 30% of its immunological activity suggested that the modified protein contained antibody recognizable residual native structure, which presumably accommodates some antigen

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03483.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The N‐terminal sequences of two calf‐thymus non‐histone chromosomal proteins, HMG‐1 and HMG‐2, are compared. Both N‐terminal sequences are basic, and differ at only one position. This contrasts with the C‐terminal portion of HMG‐1 which we have previously shown to be high in acidic residues. There is no obvious sequence homology with any of the known sequences

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03484.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The primary structure of collagen is characterized by the repeating tripeptide sequence (Gly‐R2‐R3)n. The results of theoretical studies, carried out using contact criteria to compute the stereochemically allowed orientations for various side chains at locations 2 and 3, are reported here. It is found that side chains with only γ‐atoms, as in valine, serine and threonine, or with only one δ‐methyl group, as in isoleucine, can occur equally well at locations 2 and 3, as is actually the case in collagen. Side chains with two Cδ‐atoms, as in leucine and phenyl‐alanine, can also be accommodated at both positions. However, if they occur as R3their freedom of orientation is severely restricted in the presence of a proline residue as R2in a neighbouring chain.If water molecules bound to the chains of the triple helix are assumed to be present, then location 3 is virtually impossible for leucine and phenylalanine residues. Location 2 is, however, unaffected, and their presence as R2can help to shield the water molecules from disturbance by the solvent medium. This may be the reason for the preferential occurrence of Leu and Phe residues in location 2 in the collagen triplets, although the polypeptides (Gly‐Pro‐Leu)nand (Gly‐Pro‐Phe)nform co

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03485.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY