Redesigning channel-forming peptides: amino acid substitutions that enhance rates of supramolecular self-assembly and raise ion transport activity.
Three series of 22-residue peptides derived from the transmembrane M2 segment of the glycine receptor alpha1-subunit (M2GlyR) have been designed, synthesized, and tested to determine the plasticity of a channel-forming sequence and to define whether channel pores with enhanced conductive properties could be created. Sixteen sequences were examined for aqueous solubility, solution-association tendency, secondary structure, and half-maximal concentration for supramolecular assembly, channel activity, and ion transport properties across epithelial monolayers. All peptides interact strongly with membranes: associating with, inserting across, and assembling to form homooligomeric bundles when in micromolar concentrations. Single and double amino acid replacements involving arginine and/or aromatic amino acids within the final five C-terminal residues of the peptide cause dramatic effects on the concentration dependence, yielding a range of K1/2 values from 36 +/- 5 to 390 +/- 220 microM for transport activity. New water/lipid interfacial boundaries were established for the transmembrane segment using charged or aromatic amino acids, thus limiting the peptides' ability to move perpendicularly to the plane of the bilayer. Formation of discrete water/lipid interfacial boundaries appears to be necessary for efficient supramolecular assembly and high anion transport activity. A peptide sequence is identified that may show efficacy in channel replacement therapy for channelopathies such as cystic fibrosis.
Shank
Lalida P
LP
Department of Biochemistry, and Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas 66506, USA.
Broughman
James R
JR
Takeguchi
Wade
W
Cook
Gabriel
G
Robbins
Ashley S
AS
Hahn
Lindsey
L
Radke
Gary
G
Iwamoto
Takeo
T
Schultz
Bruce D
BD
Tomich
John M
JM
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D002460:Cell Line; D019281:Dimerization; D004285:Dogs; D015640:Ion Channel Gating / Q000502:physiology*; D007668:Kidney / Q000737:chemistry* / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry*; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D015202:Protein Engineering / Q000379:methods*; D018009:Receptors, Glycine / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship
D008051:Lipid Bilayers; D046912:Multiprotein Complexes; D018009:Receptors, Glycine