title: Biophysical Characterization of Human Protamine-1 as a Responsive CEST MR Contrast Agent.
abstract: The protamines are a low-molecular-weight, arginine-rich family of nuclear proteins that protect chromosomal DNA in germ cells by packing it densely using electrostatic interactions. Human protamine-1 (hPRM1) has been developed as a magnetic resonance imaging (MRI) chemical exchange saturation transfer (CEST) reporter gene, based on a sequence that is approximately 50% arginine, which has a side chain with rapidly exchanging protons. In this study, we have synthesized hPRM1 and determined how its CEST MRI contrast varies as a function of pH, phosphorylation state, and upon noncovalent interaction with nucleic acids and heparin (as antagonist). CEST contrast was found to be highly sensitive to phosphorylation on serine residues, intra- and intermolecular disulfide bridge formation, and the binding of negatively charged nucleotides and heparin. In addition, the nucleotide binding constants (Keq) for the protamines were determined through plotting the molar concentration of heparin versus CEST contrast and compared between hPRM1 and salmon protamine. Taken together, these findings are important for explaining the CEST contrast of existing arginine-rich probes as well as serving as a guideline for designing new genetic or synthetic probes.
authors: Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine , Baltimore, Maryland United States ; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute , Baltimore, Maryland United States.
authors: Nikita
authors: N
authors: Oskolkov
authors: Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine , Baltimore, Maryland United States ; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering , Baltimore, Maryland United States.
authors: Amnon
authors: A
authors: Bar-Shir
authors: Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine , Baltimore, Maryland United States ; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute , Baltimore, Maryland United States ; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering , Baltimore, Maryland United States.
authors: Kannie W Y
authors: KW
authors: Chan
authors: Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine , Baltimore, Maryland United States ; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute , Baltimore, Maryland United States.
authors: Xiaolei
authors: X
authors: Song
authors: Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine , Baltimore, Maryland United States ; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute , Baltimore, Maryland United States.
authors: Peter C M
authors: PC
authors: van Zijl
authors: Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine , Baltimore, Maryland United States ; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute , Baltimore, Maryland United States ; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering , Baltimore, Maryland United States.
authors: Jeff W M
authors: JW
authors: Bulte
authors: Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine , Baltimore, Maryland United States ; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute , Baltimore, Maryland United States ; Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering , Baltimore, Maryland United States.
authors: Assaf A
authors: AA
authors: Gilad
authors: Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine , Baltimore, Maryland United States ; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute , Baltimore, Maryland United States.
authors: Michael T
authors: MT
authors: McMahon
references: Neuroimage. 2012 Jan 16;59(2):1004-12
references: 21939774
references: Hum Reprod Update. 2007 May-Jun;13(3):313-27
references: 17208950
references: Gene Ther. 1997 Sep;4(9):961-8
references: 9349433
references: J Biol Chem. 2004 May 7;279(19):20088-95
references: 14990583
references: Curr Opin Neurol. 2011 Aug;24(4):386-93
references: 21734576
references: Magn Reson Med. 2012 Dec;68(6):1919-23
references: 23023588
references: Contrast Media Mol Imaging. 2010 May-Jun;5(3):162-70
references: 20586030
references: J Am Chem Soc. 2013 Jan 30;135(4):1617-24
references: 23289583
references: J Am Chem Soc. 2011 Oct 19;133(41):16326-9
references: 21919523
references: J Am Chem Soc. 2001 Sep 5;123(35):8628-9
references: 11525684
references: Nat Biotechnol. 2000 Mar;18(3):321-5
references: 10700150
references: ACS Chem Biol. 2014 Jan 17;9(1):134-8
references: 24138139
references: Radiology. 2003 Aug;228(2):480-7
references: 12819345
references: Angew Chem Int Ed Engl. 2005 Oct 28;44(42):6920-3
references: 16206314
references: Proc Natl Acad Sci U S A. 2004 Jul 27;101(30):10901-6
references: 15256592
references: Nat Protoc. 2013 Dec;8(12):2380-91
references: 24177294
references: J Control Release. 2014 Apr 28;180:51-9
references: 24548481
references: Nat Med. 2013 Aug;19(8):1067-72
references: 23832090
references: Genome Biol. 2007;8(9):227
references: 17903313
references: Biomaterials. 2014 Sep;35(27):7811-8
references: 24930848
references: Q Rev Biophys. 2007 Nov;40(4):287-326
references: 18405419
references: J Theor Biol. 2006 Aug 7;241(3):533-40
references: 16442565
references: J Am Chem Soc. 2013 May 1;135(17):6396-8
references: 23601132
references: Nat Med. 2006 Jan;12(1):144-8
references: 16380717
references: Neuroimage. 2011 Feb 1;54(3):2079-85
references: 20951217
references: Proc Natl Acad Sci U S A. 2007 Mar 13;104(11):4359-64
references: 17360529
references: Proc Natl Acad Sci U S A. 2008 Feb 19;105(7):2266-70
references: 18268341
references: Nat Biotechnol. 2010 Mar;28(3):264-70
references: 20190737
references: Biochim Biophys Acta. 1993 Nov 10;1203(1):109-14
references: 8218377
references: J Am Chem Soc. 2010 Oct 13;132(40):14002-3
references: 20853833
references: Magn Reson Med. 2006 Jan;55(1):23-9
references: 16342157
references: Biol Proced Online. 2009 May 15;11:32-51
references: 19495910
references: Nat Med. 2007 Apr;13(4):498-503
references: 17351627
references: J Biol Chem. 1975 Jan 10;250(1):39-45
references: 1141210
references: Nat Mater. 2013 Mar;12(3):268-75
references: 23353626
references: Biochim Biophys Acta. 1978 May 23;518(3):440-9
references: 656427
references: Magn Reson Med. 2008 Oct;60(4):803-12
references: 18816830
references: Proteins. 1990;7(3):205-14
references: 2194218
references: Nat Biotechnol. 2005 Aug;23(8):983-7
references: 16041364
references: Ontogenez. 2012 Mar-Apr;43(2):143-53
references: 22650080
references: Nat Biotechnol. 2007 Feb;25(2):217-9
references: 17259977
references: NMR Biomed. 2014 Mar;27(3):320-31
references: 24395616