PDBsum entry 1cb3

Molten globule state

PDB id: 1cb3

Contents

Protein chain

13 a.a.

PDB id:

1cb3

Name:

Molten globule state

Title:

Local interactions drive the formation of non-native structure in the denatured state of human alpha-lactalbumin: a high resolution structural characterization of a peptide model in aqueous solution

Structure:

Lca. Chain: a. Engineered: yes. Mutation: yes. Other_details: acetylated n-terminus amidated c-terminus

Source:

Synthetic: yes. Homo sapiens. Human. Organism_taxid: 9606. Other_details: the peptide was chemically synthesized.

NMR struc:

40 models

Authors:

S.J.Demarest,Y.Hua,D.P.Raleigh

Key ref:

S.J.Demarest et al. (1999). Local interactions drive the formation of nonnative structure in the denatured state of human alpha-lactalbumin: a high resolution structural characterization of a peptide model in aqueous solution. Biochemistry, 38, 7380-7387. PubMed id: 10353850 DOI: 10.1021/bi990320z

Date:

26-Feb-99 Release date: 08-Jun-99

Protein chain

P00709  (LALBA_HUMAN) -  Alpha-lactalbumin from Homo sapiens

Seq: 142 a.a.

Struc: 12 a.a.*

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

DOI no: 10.1021/bi990320z

Biochemistry 38:7380-7387 (1999)

PubMed id: 10353850

Local interactions drive the formation of nonnative structure in the denatured state of human alpha-lactalbumin: a high resolution structural characterization of a peptide model in aqueous solution.

S.J.Demarest, Y.Hua, D.P.Raleigh.

ABSTRACT

There are a small number of peptides derived from proteins that have a propensity to adopt structure in aqueous solution which is similar to the structure they possess in the parent protein. There are far fewer examples of protein fragments which adopt stable nonnative structures in isolation. Understanding how nonnative interactions are involved in protein folding is crucial to our understanding of the topic. Here we show that a small, 11 amino acid peptide corresponding to residues 101-111 of the protein alpha-lactalbumin is remarkably structured in isolation in aqueous solution. The peptide has been characterized by 1H NMR, and 170 ROE-derived constraints were used to calculate a structure. The calculations yielded a single, high-resolution structure for residues 101-107 that is nonnative in both the backbone and side-chain conformations. In the pH 6.5 crystal structure, residues 101-105 are in an irregular turn-like conformation and residues 106-111 form an alpha-helix. In the pH 4.2 crystal structure, residues 101-105 form an alpha-helix, and residues 106-111 form a loopike structure. Both of these structures are significantly different from the conformation adopted by our peptide. The structure in the peptide model is primarily the result of local side-chain interactions that force the backbone to adopt a nonnative 310/turn-like structure in residues 103-106. The structure in aqueous solution was compared to the structure in 30% trifluoroethanol (TFE), and clear differences were observed. In particular, one of the side-chain interactions, a hydrophobic cluster involving residues 101-105, is different in the two solvents and residues 107-111 are considerably more ordered in 30% TFE. The implications of the nonnative structure for the folding of alpha-lactalbumin is discussed.