title: The rod transducin alpha subunit amino terminus is heterogeneously fatty acylated.
abstract: Rod transducin (Tr), a heterotrimeric GTP-binding protein composed of alpha, beta, and gamma subunits, couples photolysis of rhodopsin to the activation of cyclic GMP phosphodiesterase in the vertebrate visual signal transduction cascade. To determine if T alpha r is covalently modified, we analyzed tryptic fragments of bovine retinal T alpha r using electrospray mass spectrometry, liquid chromatography/mass spectrometry, tandem mass spectrometry, and gas chromatography. A novel heterogeneous fatty acylation was detected at the NH2 terminus. Four types of NH2-terminal tryptic fragments of T alpha r were isolated, and each contained either a lauroyl (C12:0), myristoyl (C14:0), (cis-delta 5)-tetradecaenoyl (C14:1) or (cis,cis-delta 5, delta 8)-tetradecadienoyl (C14:2) fatty acyl residue amide-linked to the NH2-terminal glycine residue. NH2-terminal fatty acylation does not anchor T alpha r permanently in the membrane, since T alpha r used in these experiments was eluted without detergent from rod outer segment membranes.
authors.affiliation: Howard Hughes Medical Institute, University of Washington, Seattle 98195.
authors.forename: T A
authors.initials: TA
authors.lastname: Neubert
authors.forename: R S
authors.initials: RS
authors.lastname: Johnson
authors.forename: J B
authors.initials: JB
authors.lastname: Hurley
authors.forename: K A
authors.initials: KA
authors.lastname: Walsh
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000378:metabolism; D000215:Acylation; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D004789:Enzyme Activation; D005227:Fatty Acids / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D015398:Signal Transduction; D013056:Spectrophotometry, Ultraviolet; D015293:Transducin / Q000235:genetics* / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D015293:Transducin