A spectroscopic study of the mitochondrial transit peptide of rat malate dehydrogenase.
A peptide corresponding to the N-terminal sequence of the rat malate dehydrogenase, comprising the transit sequence and two residues of the mature protein (MLSALARPVGAALR-RSFSTSAQNNAK) has been chemically synthesized, and its structural characteristics investigated by Fourier-transform i.r. (FT-IR), c.d. and 1H-n.m.r. spectroscopy. FT-IR and c.d. spectra of the peptide were recorded in a variety of environments (aqueous solution, trifluoroethanol) and after incorporation into phospholipid bilayers. The peptide was found to be mainly in aperiodic or undefined conformation in aqueous solution. However, in trifluoroethanol a marked increase in alpha-helical content was observed. An increase in alpha-helical content was also observed in negatively charged lipids (dimyristoylphosphatidylglycerol and cardiolipin). However, when reconstituted in a zwitterionic phospholipid (dimyristoylphosphatidylcholine), no alpha-helical structure was observed. N.m.r. spectroscopy was used to characterize the helical structure in greater detail in trifluoroethanol. The 1H-n.m.r. spectrum of the peptide in this solvent was assigned using standard homonuclear two-dimensional methods. The observed patterns of nuclear Overhauser enhancements confirmed the deductions obtained from c.d. and FT-1R spectroscopy concerning the solution conformation, suggesting a region of flexible nascent helix between Ala-4 and Ser-18. This structure is discussed in terms of the possible function of the peptide.
SmithKline Beecham Pharmaceuticals, Welwyn, Herts, U.K.
L K
LK
MacLachlan
P I
PI
Haris
D G
DG
Reid
J
J
White
D
D
Chapman
J A
JA
Lucy
B M
BM
Austen
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001693:Biological Transport, Active; D002308:Cardiolipins / Q000378:metabolism; D002942:Circular Dichroism; D003198:Computer Simulation; D008051:Lipid Bilayers / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008291:Malate Dehydrogenase / Q000737:chemistry* / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000378:metabolism; D017433:Protein Structure, Secondary; D051381:Rats; D012015:Reference Standards; D012694:Serine / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014270:Trifluoroethanol / Q000737:chemistry
D002308:Cardiolipins; D008051:Lipid Bilayers; D010446:Peptide Fragments; D010455:Peptides; D010715:Phosphatidylglycerols; D012694:Serine; D014270:Trifluoroethanol; C002773:dimyristoylphosphatidylglycerol; D008291:Malate Dehydrogenase; D000409:Alanine