Protein structure and function
4114 Molecular Biology Building
Dept. of Biochemistry, Biophysics & Molecular Biology
Iowa State University
Ames, IA 50011
Phone: (515) 294-2616
B.S., Chemistry and Biology, University of Nebraska, 1992
Ph.D., Biochemistry, Rice University, 1995
Postdoctoral Fellow, Rice University, 1995-1998
Research in the Hargrove laboratory involves the structure, function, folding, and expression of heme proteins. Heme proteins exhibit marked differences in reactivity toward diatomic ligands such as O2, CO, and NO, all of which are important biological molecules. However, unlike most enzymatic reactions which rely on the exact shape and charge distribution of the substrate molecule to determine specificity, selective recognition of small diatomic ligands by heme proteins occurs after the heme-ligand complex is formed.
Myoglobin and hemoglobin have long been ideal systems for developing an understanding of the relationship between the structure and function of proteins. More recently, these proteins have found renewed interest due to the application of modern methods of time-resolved crystallography, site-directed mutagenesis, and molecular dynamics to explore molecular recognition and ligand binding with high resolution. Furthermore, heme proteins which are less understood physiologically and biophysically have been discovered which appear to have a wide variety of novel signaling and oxygen storage functions. My laboratory uses site-directed mutagenesis, kinetic and spectroscopic methods, and X-ray crystallography to study the high resolution structure and function of heme proteins. There are three projects currently underway:
1. Structure and function of plant hemoglobins. Plants contain two kinds of hemoglobins. Those that fix nitrogen in symbiosis with bacteria have oxygen transport (leg)hemoglobins, and all plants have nonsymbiotic hemoglobins whose function likely relate to molecular signaling and scavenging. We are interested in the latter group of proteins because their structures are unusual, having bis-histidyl coordinating of the heme iron. Our goal is to understand how these “hexacoordinate” hemoglobins are able to bind ligands like oxygen, nitric oxide, and carbon monoxide in spite of intramolecular competition from a histidine side chain. Eventually we would like to relate their chemical behavior to physiological function. Our interest in leghemoglobins is centered on a goal of understanding the evolution of oxygen transport in plants. The leghemoglobins evolved from nonsymbiotic hemoglobins ~ 200 million years ago, and we are using biophysical methods to investigate the structural events that led to this important event in evolution.
2. Structure and function of human hexacoordinate hemoglobins. Humans contain two hexacoordinate hemoglobins; neuroglobin and cytoglobin. We are interesting in their structure, ligand binding behavior, and potential structural and functional relationships to hexacoordinate plant hemoglobins. Neuroglobin is found in neural tissue and the retina. Cytoglobin is found in many tissues. Likely functions of these proteins include signaling and NO scavenging. Our goals are to use structure and biophysics to decipher potential functions and understand the chemical role of hexacoordination in these systems.
3. Bacterial hexacoordinate hemoglobins. Some cyanobacteria also contain hexacoordinate hemoglobins. These proteins are unusual in having a covalent bond between a His side chain and a heme vinyl. We are investigating the role of this covalent bond along with the structure and function of these proteins. Furthermore, this organism is readily amenable to genetic manipulation so we are working toward understanding physiological function using reverse genetic methods.
1: Bandow N, Gilles VS, Freesmeier B, Semrau JD, Krentz B, Gallagher W,
McEllistrem MT, Hartsel SC, Choi DW, Hargrove MS, Heard TM, Chesner LN,
Braunreiter KM, Cao BV, Gavitt MM, Hoopes JZ, Johnson JM, Polster EM, Schoenick
BD, Umlauf AM, DiSpirito AA. Spectral and copper binding properties of
methanobactin from the facultative methanotroph Methylocystis strain SB2. J Inorg
Biochem. 2012 May;110:72-82. doi: 10.1016/j.jinorgbio.2012.02.002. Epub 2012 Feb
12. PubMed PMID: 22504273.
2: Sturms R, DiSpirito AA, Fulton DB, Hargrove MS. Hydroxylamine reduction to
ammonium by plant and cyanobacterial hemoglobins. Biochemistry. 2011 Dec
20;50(50):10829-35. doi: 10.1021/bi201425f. Epub 2011 Nov 18. PubMed PMID:
3: Sturms R, DiSpirito AA, Hargrove MS. Plant and cyanobacterial hemoglobins
reduce nitrite to nitric oxide under anoxic conditions. Biochemistry. 2011 May
17;50(19):3873-8. doi: 10.1021/bi2004312. Epub 2011 Apr 20. PubMed PMID:
4: Kakar S, Sturms R, Tiffany A, Nix JC, DiSpirito AA, Hargrove MS. Crystal
structures of Parasponia and Trema hemoglobins: differential heme coordination is
linked to quaternary structure. Biochemistry. 2011 May 24;50(20):4273-80. doi:
10.1021/bi2002423. Epub 2011 Apr 27. PubMed PMID: 21491905.
5: Kakar S, Hoffman FG, Storz JF, Fabian M, Hargrove MS. Structure and reactivity
of hexacoordinate hemoglobins. Biophys Chem. 2010 Nov;152(1-3):1-14. doi:
10.1016/j.bpc.2010.08.008. Epub 2010 Sep 21. Review. PubMed PMID: 20933319.
6: Bose S, Adhikary R, Barnes CA, Fulton DB, Hargrove MS, Song X, Petrich JW.
Comparison of the dielectric response obtained from fluorescence upconversion
measurements and molecular dynamics simulations for coumarin 153-apomyoglobin
complexes and structural analysis of the complexes by NMR and fluorescence
methods. J Phys Chem A. 2011 Apr 28;115(16):3630-41. doi: 10.1021/jp1008225. Epub
2010 May 6. PubMed PMID: 20446696.
7: Sturms R, Kakar S, Trent J 3rd, Hargrove MS. Trema and parasponia hemoglobins
reveal convergent evolution of oxygen transport in plants. Biochemistry. 2010 May
18;49(19):4085-93. doi: 10.1021/bi1002844. PubMed PMID: 20377207.
8: Smagghe BJ, Hoy JA, Percifield R, Kundu S, Hargrove MS, Sarath G, Hilbert JL,
Watts RA, Dennis ES, Peacock WJ, Dewilde S, Moens L, Blouin GC, Olson JS, Appleby
CA. Review: correlations between oxygen affinity and sequence classifications of
plant hemoglobins. Biopolymers. 2009 Dec;91(12):1083-96. doi: 10.1002/bip.21256.
PubMed PMID: 19441024.
9: Ostojić J, Grozdanić SD, Syed NA, Hargrove MS, Trent JT 3rd, Kuehn MH, Kwon
YH, Kardon RH, Sakaguchi DS. Patterns of distribution of oxygen-binding globins,
neuroglobin and cytoglobin in human retina. Arch Ophthalmol. 2008
Nov;126(11):1530-6. doi: 10.1001/archopht.126.11.1530. PubMed PMID: 19001220.
10: Ostojic J, Grozdanic S, Syed NA, Hargrove MS, Trent JT 3rd, Kuehn MH, Kardon
RH, Kwon YH, Sakaguchi DS. Neuroglobin and cytoglobin distribution in the
anterior eye segment: a comparative immunohistochemical study. J Histochem
Cytochem. 2008 Sep;56(9):863-72. doi: 10.1369/jhc.2008.951392. Epub 2008 Jun 23.
PubMed PMID: 18574250; PubMed Central PMCID: PMC2516955.
11: Smagghe BJ, Trent JT 3rd, Hargrove MS. NO dioxygenase activity in hemoglobins
is ubiquitous in vitro, but limited by reduction in vivo. PLoS One. 2008 Apr
30;3(4):e2039. doi: 10.1371/journal.pone.0002039. PubMed PMID: 18446211; PubMed
Central PMCID: PMC2323109.
12: Hoy JA, Hargrove MS. The structure and function of plant hemoglobins. Plant
Physiol Biochem. 2008 Mar;46(3):371-9. doi: 10.1016/j.plaphy.2007.12.016. Epub
2008 Jan 3. Review. PubMed PMID: 18321722.
13: Halder M, Mukherjee P, Bose S, Hargrove MS, Song X, Petrich JW. Solvation
dynamics in protein environments: comparison of fluorescence upconversion
measurements of coumarin 153 in monomeric hemeproteins with molecular dynamics
simulations. J Chem Phys. 2007 Aug 7;127(5):055101. PubMed PMID: 17688362.
14: Hoy JA, Robinson H, Trent JT 3rd, Kakar S, Smagghe BJ, Hargrove MS. Plant
hemoglobins: a molecular fossil record for the evolution of oxygen transport. J
Mol Biol. 2007 Aug 3;371(1):168-79. Epub 2007 May 18. PubMed PMID: 17560601.
15: Hoy JA, Smagghe BJ, Halder P, Hargrove MS. Covalent heme attachment in
Synechocystis hemoglobin is required to prevent ferrous heme dissociation.
Protein Sci. 2007 Feb;16(2):250-60. PubMed PMID: 17242429; PubMed Central PMCID:
16: Halder P, Trent JT 3rd, Hargrove MS. Influence of the protein matrix on
intramolecular histidine ligation in ferric and ferrous hexacoordinate
hemoglobins. Proteins. 2007 Jan 1;66(1):172-82. PubMed PMID: 17044063.
17: Mukherjee P, Halder M, Hargrove MS, Petrich JW. Characterization of the
interactions of fluorescent probes with proteins: coumarin 153 and 1,8-ANS in
complex with holo- and apomyoglobin. Photochem Photobiol. 2006
Nov-Dec;82(6):1586-90. PubMed PMID: 16961435.
18: Smagghe BJ, Kundu S, Hoy JA, Halder P, Weiland TR, Savage A, Venugopal A,
Goodman M, Premer S, Hargrove MS. Role of phenylalanine B10 in plant nonsymbiotic
hemoglobins. Biochemistry. 2006 Aug 15;45(32):9735-45. PubMed PMID: 16893175.
19: Ostojić J, Sakaguchi DS, de Lathouder Y, Hargrove MS, Trent JT 3rd, Kwon YH,
Kardon RH, Kuehn MH, Betts DM, Grozdanić S. Neuroglobin and cytoglobin:
oxygen-binding proteins in retinal neurons. Invest Ophthalmol Vis Sci. 2006
Mar;47(3):1016-23. PubMed PMID: 16505036.
20: Choi DW, Zea CJ, Do YS, Semrau JD, Antholine WE, Hargrove MS, Pohl NL, Boyd
ES, Geesey GG, Hartsel SC, Shafe PH, McEllistrem MT, Kisting CJ, Campbell D, Rao
V, de la Mora AM, Dispirito AA. Spectral, kinetic, and thermodynamic properties
of Cu(I) and Cu(II) binding by methanobactin from Methylosinus trichosporium
OB3b. Biochemistry. 2006 Feb 7;45(5):1442-53. PubMed PMID: 16445286.