Cyclic peptide models of the Ca2+-binding loop of α-lactalbumin

Viktor Farkas, E. Vass, Ignace Hanssens, Zs. Majer, M. Hollósi

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

A series of cyclic peptides with different linkers were designed and synthesized to model the elbow-type Ca2+-binding loop of α-lactalbumin (LA). All amino acids of the Ca2+-binding loop are strikingly well conserved among LAs of different species with the sequence Lys79-Phe-Leu-Asp82-Asp-Asp-Leu-Thr- Asp 87-Asp88, where three carboxylates of Asp82, Asp87, and Asp88 and the amide carbonyl oxygen atoms of Lys79 and Asp84 participate in Ca2+ binding. Alanine-containing models were also prepared for monitoring the role of the binding (82, 87-88) and nonbinding Asp residues (83-84) in coordinating the cation. The structural features of synthetic peptides and their Ca 2+-binding properties were investigated in solution by circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy. In water, the CD curves show a strong negative band below 200 nm as a sign of the presence of unfolded conformers. In TFE, all cyclic peptides were found to have a CD spectrum, reflecting the presence of folded (turn) conformers. The effect of Ca2+ was dependent on the structure and concentration of the model and the Ca2+ to peptide ratio (rcat). A surprising time dependence of the FTIR spectra of Ca2+ complexes of the Ala-containing peptides was observed. The shape of the broad amide I band showed no more change after ∼60 min. Contrary to this, the deprotonation of the side chain COOH group(s) and formation of the final coordination sphere of Ca2+ took more time. Infrared spectra showed that in the Ca 2+ complex of model comprising the binding Asp residues of LA, the cation is coordinated to the COO- groups of all three Asps, while in the complex of model comprising nonbinding Asp residues of LA, the two neighboring Asp side chains form a bridged Ca2+-binding system.

Original languageEnglish
Pages (from-to)5310-5320
Number of pages11
JournalBioorganic and Medicinal Chemistry
Volume13
Issue number17
DOIs
Publication statusPublished - Sep 1 2005

Fingerprint

Lactalbumin
Cyclic Peptides
Viperidae
Circular Dichroism
Dichroism
Amides
Peptides
Cations
phenylalanylleucine
Polytetrafluoroethylene
Infrared radiation
Fourier Analysis
Fourier Transform Infrared Spectroscopy
Elbow
Deprotonation
Alanine
Oxygen
Fourier transforms
Amino Acids
Water

Keywords

  • α-Lactalbumin
  • Ca-binding loop
  • Circular dichroism
  • Cyclic peptides
  • FTIR

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Organic Chemistry
  • Drug Discovery
  • Pharmaceutical Science

Cite this

Cyclic peptide models of the Ca2+-binding loop of α-lactalbumin. / Farkas, Viktor; Vass, E.; Hanssens, Ignace; Majer, Zs.; Hollósi, M.

In: Bioorganic and Medicinal Chemistry, Vol. 13, No. 17, 01.09.2005, p. 5310-5320.

Research output: Contribution to journalArticle

@article{68fee457c69d4603b5326f411954f1f4,
title = "Cyclic peptide models of the Ca2+-binding loop of α-lactalbumin",
abstract = "A series of cyclic peptides with different linkers were designed and synthesized to model the elbow-type Ca2+-binding loop of α-lactalbumin (LA). All amino acids of the Ca2+-binding loop are strikingly well conserved among LAs of different species with the sequence Lys79-Phe-Leu-Asp82-Asp-Asp-Leu-Thr- Asp 87-Asp88, where three carboxylates of Asp82, Asp87, and Asp88 and the amide carbonyl oxygen atoms of Lys79 and Asp84 participate in Ca2+ binding. Alanine-containing models were also prepared for monitoring the role of the binding (82, 87-88) and nonbinding Asp residues (83-84) in coordinating the cation. The structural features of synthetic peptides and their Ca 2+-binding properties were investigated in solution by circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy. In water, the CD curves show a strong negative band below 200 nm as a sign of the presence of unfolded conformers. In TFE, all cyclic peptides were found to have a CD spectrum, reflecting the presence of folded (turn) conformers. The effect of Ca2+ was dependent on the structure and concentration of the model and the Ca2+ to peptide ratio (rcat). A surprising time dependence of the FTIR spectra of Ca2+ complexes of the Ala-containing peptides was observed. The shape of the broad amide I band showed no more change after ∼60 min. Contrary to this, the deprotonation of the side chain COOH group(s) and formation of the final coordination sphere of Ca2+ took more time. Infrared spectra showed that in the Ca 2+ complex of model comprising the binding Asp residues of LA, the cation is coordinated to the COO- groups of all three Asps, while in the complex of model comprising nonbinding Asp residues of LA, the two neighboring Asp side chains form a bridged Ca2+-binding system.",
keywords = "α-Lactalbumin, Ca-binding loop, Circular dichroism, Cyclic peptides, FTIR",
author = "Viktor Farkas and E. Vass and Ignace Hanssens and Zs. Majer and M. Holl{\'o}si",
year = "2005",
month = "9",
day = "1",
doi = "10.1016/j.bmc.2005.06.040",
language = "English",
volume = "13",
pages = "5310--5320",
journal = "Bioorganic and Medicinal Chemistry",
issn = "0968-0896",
publisher = "Elsevier Limited",
number = "17",

}

TY - JOUR

T1 - Cyclic peptide models of the Ca2+-binding loop of α-lactalbumin

AU - Farkas, Viktor

AU - Vass, E.

AU - Hanssens, Ignace

AU - Majer, Zs.

AU - Hollósi, M.

PY - 2005/9/1

Y1 - 2005/9/1

N2 - A series of cyclic peptides with different linkers were designed and synthesized to model the elbow-type Ca2+-binding loop of α-lactalbumin (LA). All amino acids of the Ca2+-binding loop are strikingly well conserved among LAs of different species with the sequence Lys79-Phe-Leu-Asp82-Asp-Asp-Leu-Thr- Asp 87-Asp88, where three carboxylates of Asp82, Asp87, and Asp88 and the amide carbonyl oxygen atoms of Lys79 and Asp84 participate in Ca2+ binding. Alanine-containing models were also prepared for monitoring the role of the binding (82, 87-88) and nonbinding Asp residues (83-84) in coordinating the cation. The structural features of synthetic peptides and their Ca 2+-binding properties were investigated in solution by circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy. In water, the CD curves show a strong negative band below 200 nm as a sign of the presence of unfolded conformers. In TFE, all cyclic peptides were found to have a CD spectrum, reflecting the presence of folded (turn) conformers. The effect of Ca2+ was dependent on the structure and concentration of the model and the Ca2+ to peptide ratio (rcat). A surprising time dependence of the FTIR spectra of Ca2+ complexes of the Ala-containing peptides was observed. The shape of the broad amide I band showed no more change after ∼60 min. Contrary to this, the deprotonation of the side chain COOH group(s) and formation of the final coordination sphere of Ca2+ took more time. Infrared spectra showed that in the Ca 2+ complex of model comprising the binding Asp residues of LA, the cation is coordinated to the COO- groups of all three Asps, while in the complex of model comprising nonbinding Asp residues of LA, the two neighboring Asp side chains form a bridged Ca2+-binding system.

AB - A series of cyclic peptides with different linkers were designed and synthesized to model the elbow-type Ca2+-binding loop of α-lactalbumin (LA). All amino acids of the Ca2+-binding loop are strikingly well conserved among LAs of different species with the sequence Lys79-Phe-Leu-Asp82-Asp-Asp-Leu-Thr- Asp 87-Asp88, where three carboxylates of Asp82, Asp87, and Asp88 and the amide carbonyl oxygen atoms of Lys79 and Asp84 participate in Ca2+ binding. Alanine-containing models were also prepared for monitoring the role of the binding (82, 87-88) and nonbinding Asp residues (83-84) in coordinating the cation. The structural features of synthetic peptides and their Ca 2+-binding properties were investigated in solution by circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy. In water, the CD curves show a strong negative band below 200 nm as a sign of the presence of unfolded conformers. In TFE, all cyclic peptides were found to have a CD spectrum, reflecting the presence of folded (turn) conformers. The effect of Ca2+ was dependent on the structure and concentration of the model and the Ca2+ to peptide ratio (rcat). A surprising time dependence of the FTIR spectra of Ca2+ complexes of the Ala-containing peptides was observed. The shape of the broad amide I band showed no more change after ∼60 min. Contrary to this, the deprotonation of the side chain COOH group(s) and formation of the final coordination sphere of Ca2+ took more time. Infrared spectra showed that in the Ca 2+ complex of model comprising the binding Asp residues of LA, the cation is coordinated to the COO- groups of all three Asps, while in the complex of model comprising nonbinding Asp residues of LA, the two neighboring Asp side chains form a bridged Ca2+-binding system.

KW - α-Lactalbumin

KW - Ca-binding loop

KW - Circular dichroism

KW - Cyclic peptides

KW - FTIR

UR - http://www.scopus.com/inward/record.url?scp=22844448546&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=22844448546&partnerID=8YFLogxK

U2 - 10.1016/j.bmc.2005.06.040

DO - 10.1016/j.bmc.2005.06.040

M3 - Article

C2 - 16046135

AN - SCOPUS:22844448546

VL - 13

SP - 5310

EP - 5320

JO - Bioorganic and Medicinal Chemistry

JF - Bioorganic and Medicinal Chemistry

SN - 0968-0896

IS - 17

ER -