The multiple conformational charge states of zinc(II) coordination by 2His-2Cys oligopeptide investigated by ion mobility-mass spectrometry, density functional theory and theoretical collision cross sections.
Whether traveling wave ion mobility-mass spectrometry (IM-MS), B3LYP/LanL2DZ density functional theory, and ion size scaled Lennard-Jones (LJ) collision cross sections (CCS) from the B3LYP optimized structures could be used to determine the type of Zn(II) coordination by the oligopeptide acetyl-His1-Cys2-Gly3-Pro4-Tyr5-His6-Cys7(amb5) was investigated. The IM-MS analyses of a pH titration of molar equivalents of Zn(II):amb5showed that both negatively and positively charged complexes formed and coordination of Zn(II) increased as the His and Cys deprotonated near their pKa values. The B3LYP method was used to generate a series of alternative coordination structures to compare with the experimental results. The method predicted that the single negatively charged complex coordinated Zn(II) in a distorted tetrahedral geometry via the 2His-2Cys substituent groups, whereas, the double negatively charged and positively charged complexes coordinated Zn(II) via His, carbonyl oxygens and the C-terminus. The CCS of the B3LYP complexes were calculated using the LJ method and compared with those measured by IM-MS for the various charge state complexes. The LJ method provided CCS that agreed with five of the alternative distorted tetrahedral and trigonal bipyramidal coordinations for the doubly charged complexes, but provided CCS that were 15 to 31 Å2larger than those measured by IM-MS for the singly charged complexes. Collision-induced dissociation of the Zn(II) complexes and a further pH titration study of amb5B, which included amidation of the C-terminus, suggested that the 2His-2Cys coordination was more significant than coordinations that included the C-terminus. Copyright © 2016 John Wiley & Sons, Ltd.
Department of Chemistry, Texas A&M University-Commerce, Commerce, TX, 75428, USA.
Stephanie M
SM
Wagoner
Department of Chemistry, Texas A&M University-Commerce, Commerce, TX, 75428, USA.
Manogna
M
Deeconda
Department of Chemistry, Texas A&M University-Commerce, Commerce, TX, 75428, USA.
Kayleah L
KL
Cumpian
Department of Chemistry, Texas A&M University-Commerce, Commerce, TX, 75428, USA.
Rafael
R
Ortiz
Department of Chemistry, Texas A&M University-Commerce, Commerce, TX, 75428, USA.
Swetha
S
Chinthala
Department of Chemistry, Texas A&M University-Commerce, Commerce, TX, 75428, USA.
Laurence A
LA
Angel
D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D006639:Histidine / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D008958:Models, Molecular; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism*; D016335:Zinc Fingers
D009842:Oligopeptides; D006639:Histidine; D015032:Zinc; D003545:Cysteine
B3LYP/LanL2DZ; Zn(II) coordination; Zn(II)-binding peptide; collision cross sections; ion mobility-mass spectrometry; ion size scaled Lennard-Jones; zinc finger