Wyniki wyszukiwania

1

A comparative CD and fluorescence study of a series of model calcium-binding peptides

100%

Goch G., Kozlowska H., Wojtowicz A., Bierzynski A.

Acta Biochimica Polonica

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1999

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tom 46

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nr 3

Lanthanide-saturated peptides analogous to calcium-binding loops of EF-hand proteins can be used to stabilize the α-helical structure of peptide or protein segments attached to their C-termini. To study conformational properties of such loop-containing hybrids it is necessary to produce them in bacteria. In peptides obtained in this way the helix will be destabilized by the negatively charged C-terminal α-carboxyl groups. We propose to blocke them by the homoserine lactone. The results presented in this paper indicate that the presence of the lactone even at the C-terminus of the loop does not have any negative effect on the loop helix-nucleation ability. On the other hand, the presence of the α-NH+3 at the loop N-terminus leads to a drop of metal-binding constant and loss of the rigid structure of the α-helical segment of the loop. The α-amino group separated by one glycine residue from the loop N-terminus should also be avoided because it perturbs the conformation of the N-terminal part of the loop and may reduce the loop affinity to lanthanide ions.

2

Folding initiation sites and protein folding

86%

Dadlez M.

Acta Biochimica Polonica

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1999

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tom 46

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nr 3

The paper discusses the role of local structural preferences of protein segments in the folding of proteins. First a short overview of the local, secondary structures detected in peptides, protein fragments, denatured proteins and early folding intermediates is given. Next the discussion of their role in protein folding is presented based on recent literature and data obtained in our laboratory. In conclusion it is pointed out that, during folding, local structures populated at low levels in denatured state may facilitate the crossing of the folding transition state barrier, and consequently accelerate the rate limiting step in folding. However, the data show that this effect does not follow simple rules.

3

Helix-coil transition theories. Are they correct?

86%

Bierzynski A., Pawlowski K.

Acta Biochimica Polonica

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1997

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tom 44

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nr 3

Principles of contemporary theoretical description of a-helix formation by polypeptide chains in water solution are shortly presented and critically discussed. The theory treats the unfolded state of a peptide as "random coil" — an ideal conformation quite distant from reality. We suggest that for this reason the helix propagation parameters of amino-acid residues, determined using series of model peptides with different sequential patterns, are not the same. Interpretation of the so called "nucleation parameter" is erroneous. In fact, it is not determined by the helix nucleation process but rather by a specific situation of residues at the helix N- and C-termini, and it strongly depends on solvation of their NH and CO groups, respectively. Consequently, helical segments with terminal sequences dominated by residues with strongly hydrophobic, bulky side chains can be very unstable. We postulate that an unexpectedly high stability of very short, pre-nucleated helices studied by us arises from a "helix end separation effect": separated helix termini are better solvated than when they overlap each other. Because of this effect, helix initiation may be much more difficult than predicted by the theoretical "helix nucleation parameters".

4

Synthesis, physicochemical and biological properties of poly-alpha-amino acids - the simplest of protein models

58%

Katchalski-Katzir E.

Acta Biochimica Polonica

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1996

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tom 43

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nr 1

During the 1950s, linear and multichain poly-a-amino acids were synthesized by polymerization of the corresponding N-carboxy-amino acid anhydrides in solution in the presence of suitable catalysts. The resulting homo- and heteropolymers have since been widely employed as simple protein models. Under appropriate conditions, poly-a-amino acids, in the solid state and in solution, were found to acquire conformations of an a-helix and of (^-parallel and antiparallel pleated sheets, or to exist as random coils. Their use in experimental and theoretical investigations of helix-coil transitions helped to shed new light on the mechanisms involved in protein denaturation. Poly-a-amino acids played an important role in the deciphering of the genetic code. In addition, analysis of the antigenicity of poly-a-amino acids led to the elucidation of the factors determining the antigenicity of proteins and peptides. Interest in the biological and physicochemical characteristics of poly-a-amino acids was recently renewed because of the reported novel findings that some copolymers of amino acids are effective as drugs in multiple sclerosis, and that glutamine repeats and reiteration of other amino acids occur in inherited neurodegenerative diseases. The presence of repeating sequences of amino acids in proteins, and of nucleotides in DNA, raises many interesting questions about their respective roles in determining protein structure and function, and gene performance and regulation.

Ograniczanie wyników

4 Acta Biochimica Polonica

2 Bierzynski A.

1 Dadlez M.

1 Goch G.

1 Katchalski-Katzir E.

1 Kozlowska H.

1 Pawlowski K.

1 Wojtowicz A.

2 1999

1 1997

1 1996

A comparative CD and fluorescence study of a series of model calcium-binding peptides

Folding initiation sites and protein folding

Helix-coil transition theories. Are they correct?

Synthesis, physicochemical and biological properties of poly-alpha-amino acids - the simplest of protein models