1NKF

CALCIUM-BINDING PEPTIDE, NMR, 30 STRUCTURES

Summary for 1NKF

• Entry DOI: 10.2210/pdb1nkf/pdb
• Descriptor: CALCIUM-BINDING HEXADECAPEPTIDE, LANTHANUM (III) ION (2 entities in total)
• Functional Keywords: ef hand calcium binding loop, alpha-helix, calcium-binding
• Biological source: Homo sapiens (human)
• Cellular location: Cytoplasm, cytoskeleton, spindle: P02593
• Total number of polymer chains: 1
• Total formula weight: 1745.55

Authors

Sticht, H.,Ejchart, A. (deposition date: 1998-03-09, release date: 1999-02-16, Last modification date: 2024-10-30)

Primary citation

Siedlecka, M.,Goch, G.,Ejchart, A.,Sticht, H.,Bierzyski, A.
Alpha-helix nucleation by a calcium-binding peptide loop.
Proc.Natl.Acad.Sci.USA, 96:903-908, 1999

PubMed Abstract: A 12-residue peptide AcDKDGDGYISAAENH2 analogous to the third calcium-binding loop of calmodulin strongly coordinates lanthanide ions (K = 10(5) M-1). When metal saturated, the peptide adopts a very rigid structure, the same as in the native protein, with three last residues AAE fixed in the alpha-helical conformation. Therefore, the peptide provides an ideal helix nucleation site for peptide segments attached to its C terminus. NMR and CD investigations of peptide AcDKDGDGYISAAEAAAQNH2 presented in this paper show that residues A13-Q16 form an alpha-helix of very high stability when the La3+ ion is bound to the D1-E12 loop. In fact, the lowest estimates of the helix content in this segment give values of at least 80% at 1 degreesC and 70% at 25 degreesC. This finding is not compatible with existing helix-coil transition theories and helix propagation parameters, s, reported in the literature. We conclude, therefore, that the initial steps of helix propagation are characterized by much larger s values, whereas helix nucleation is even more unfavorable than is believed. In light of our findings, thermodynamics of the nascent alpha-helices is discussed. The problem of CD spectra of very short alpha-helices is also addressed.

PubMed: 9927666
DOI: 10.1073/pnas.96.3.903

Experimental method

SOLUTION NMR