title: Spectroscopic characterization of the EF-hand domain of phospholipase C delta1: identification of a lipid interacting domain.
abstract: The interaction of the isolated EF-hand domain of phospholipase C delta1 with arachidonic acid (AA) was characterized using circular dichroism (CD) and fluorescence spectroscopy. The far-UV CD spectral changes indicate that AA binds to the EF domain. The near-UV CD spectra suggest that the orientations of aromatic residues in the peptide are affected when AA binds to the protein. The fluorescence of the single intrinsic tryptophan located in EF1 was enhanced by the addition of dodecylmaltoside (DDM) and AA suggesting that this region of the protein is involved in hydrophobic interactions. In the presence of a low concentration of DDM it was found that AA induced a change in fluorescence resonance energy transfer, which is indicative of a conformational change. The lipid induced conformational change may play a role in calcium binding because the isolated EF-hand domain did not bind Ca2+ in the absence of lipids, but Ca2+-dependent changes in the intrinsic tryptophan emission were observed when free fatty acids were present. These studies identify specific EF-hand domains as allosteric regulatory domains that require hydrophobic ligands such as lipids.
authors.affiliation: Department of Pathology, Northwestern University, The Feinberg School of Medicine, 303 East Chicago Ave, Chicago, IL 60611, USA.
authors.forename: Minae
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Zygmunt
authors.initials: Z
authors.lastname: Gryczynski
authors.forename: Joanna
authors.initials: J
authors.lastname: Lukomska
authors.forename: Jianwen
authors.initials: J
authors.lastname: Feng
authors.forename: Mary F
authors.initials: MF
authors.lastname: Roberts
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Lakowicz
authors.forename: Jon W
authors.initials: JW
authors.lastname: Lomasney
mesh_terms: D000595:Amino Acid Sequence; D016718:Arachidonic Acid / Q000378:metabolism*; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002942:Circular Dichroism; D020832:EF Hand Motifs / Q000502:physiology*; D004789:Enzyme Activation; D005960:Glucosides / Q000494:pharmacology; D057927:Hydrophobic and Hydrophilic Interactions; D007527:Isoenzymes / Q000737:chemistry*; D008024:Ligands; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D054803:Phospholipase C delta; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan / Q000737:chemistry; D010738:Type C Phospholipases / Q000737:chemistry*
chemical_list: D005960:Glucosides; D007527:Isoenzymes; D008024:Ligands; D008055:Lipids; D016718:Arachidonic Acid; C040358:dodecyl maltoside; D014364:Tryptophan; D010738:Type C Phospholipases; D054803:Phospholipase C delta; D002118:Calcium