STRUCTURAL AND FUNCTIONAL-EFFECTS OF APOLAR MUTATIONS OF THE DISTAL VALINE IN MYOGLOBIN

被引:179
作者
QUILLIN, ML
LI, TS
OLSON, JS
PHILLIPS, GN
DOU, Y
IKEDASAITO, M
REGAN, R
CARLSON, M
GIBSON, QH
LI, HY
ELBER, R
机构
[1] RICE UNIV, WM KECK CTR COMPUTAT BIOL, HOUSTON, TX 77251 USA
[2] CASE WESTERN RESERVE UNIV, SCH MED, DEPT PHYSIOL & BIOPHYS, CLEVELAND, OH 44106 USA
[3] CORNELL UNIV, BIOCHEM MOLEC & CELL BIOL SECT, ITHACA, NY 14853 USA
[4] UNIV ILLINOIS, DEPT CHEM, CHICAGO, IL 60680 USA
[5] HEBREW UNIV JERUSALEM, FRITZ HABER RES CTR, DEPT CHEM PHYS, IL-91904 JERUSALEM, ISRAEL
[6] HEBREW UNIV JERUSALEM, INST LIFE SCI, IL-91904 JERUSALEM, ISRAEL
关键词
X-RAY CRYSTALLOGRAPHY; MOLECULAR DYNAMICS; LIGAND BINDING; SITE-DIRECTED MUTAGENESIS; SPERM WHALE MYOGLOBIN;
D O I
10.1006/jmbi.1994.0034
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
High-resolution structures of the aquomet, deoxy: and CO forms of Ala68, Ile68, Leu68, and Phe68 sperm whale myoglobins have been determined by X-ray crystallography. These 12 new structures, plus those of wild-type myoglobin, have been used to interpret the effects of mutations at position 68 and the effects of cobalt substitution on the kinetics of O-2, CO, and NO binding. Molecular dynamics simulations based on crystal structures have provided information about the time-dependent behavior of photolyzed ligands for comparison with picosecond geminate recombination studies. The Val68-->Ala mutation has little effect on the structure and function of myoglobin. In Ala68 deoxymyoglobin, as in the wild-type protein, a water molecule hydrogen-bonded to the N-epsilon atom of the distal histidine restricts ligand binding and appears to be more important in regulating the function of myoglobin than direct steric interactions between the Ligand and the C-gamma atoms of the native valine side-chain. This distal pocket water molecule is displaced by the larger side-chains at position 68 in the crystal structures of Leu68 and Ile68 deoxymyoglobins. The Leu68 side-chain can rotate about its C-alpha-C-beta and C-beta-C-gamma bonds to better accommodate bound ligands, resulting in net increases in overall association rate constants and affinities due to the absence of the distal pocket water molecule. However, the flexibility of Leu68 makes simulation of picosecond NO recombination difficult since multiple starting conformations are possible. In the case of Ile68, rotation of the substituted side-chain is restricted due to branching at the beta carbon, and as a result, the delta methyl group is located close to the iron atom in both the deoxy and liganded structures. The favorable effect of displacing the distal pocket water molecule is offset by direct steric hindrance between the bound ligand and the terminal carbon atom of the isoleucine side-chain, resulting in net decreases in affinity for all three ligands and inhibition of geminate recombination which is reproduced in the molecular dynamics simulations. In Phe68 myoglobin, the benzyl side-chain is pointed away from the ligand binding site, occupying a region in the back of the distal pocket. As in wild-type and Ala68 myoglobins, a well-defined water molecule is found hydrogen bonded to the distal histidine in Phe68 deoxymyoglobin. This water molecule, in combination with the large size of the benzyl side-chain, markedly reduces the speed and extent of ligand movement into the distal pocket. Ligand movement away from the iron atom is also reduced dramatically by the Phe68 side-chain, causing large and rapid geminate recombination phases for all Ligands.
引用
收藏
页码:416 / 436
页数:21
相关论文
共 53 条
[1]   CONFORMATIONAL RELAXATION AND LIGAND-BINDING IN MYOGLOBIN [J].
ANSARI, A ;
JONES, CM ;
HENRY, ER ;
HOFRICHTER, J ;
EATON, WA .
BIOCHEMISTRY, 1994, 33 (17) :5128-5145
[2]  
BRANTLEY RE, 1993, J BIOL CHEM, V268, P6995
[3]  
BRUNGER AT, 1992, X PLOR 3 1 MANUAL
[4]   DISTAL POCKET POLARITY IN LIGAND-BINDING TO MYOGLOBIN - DEOXY AND CARBONMONOXY FORMS OF A THREONINE(68)(E11) MUTANT INVESTIGATED BY X-RAY CRYSTALLOGRAPHY AND INFRARED-SPECTROSCOPY [J].
CAMERON, AD ;
SMERDON, SJ ;
WILKINSON, AJ ;
HABASH, J ;
HELLIWELL, JR ;
LI, TS ;
OLSON, JS .
BIOCHEMISTRY, 1993, 32 (48) :13061-13070
[5]   NITRIC-OXIDE RECOMBINATION TO DOUBLE MUTANTS OF MYOGLOBIN - ROLE OF LIGAND DIFFUSION IN A FLUCTUATING HEME POCKET [J].
CARLSON, ML ;
REGAN, R ;
ELBER, R ;
LI, HY ;
PHILLIPS, GN ;
OLSON, JS ;
GIBSON, QH .
BIOCHEMISTRY, 1994, 33 (35) :10597-10606
[6]  
CARVER TE, 1992, J BIOL CHEM, V267, P14443
[7]  
CARVER TE, 1990, J BIOL CHEM, V265, P20007
[8]   ACTIVATION PARAMETERS FOR LIGAND ESCAPE FROM MYOGLOBIN PROTEINS AT ROOM-TEMPERATURE [J].
CHATFIELD, MD ;
WALDA, KN ;
MAGDE, D .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1990, 112 (12) :4680-4687
[9]  
EGEBERG KD, 1990, J BIOL CHEM, V265, P11788
[10]   ENHANCED SAMPLING IN MOLECULAR-DYNAMICS - USE OF THE TIME-DEPENDENT HARTREE APPROXIMATION FOR A SIMULATION OF CARBON-MONOXIDE DIFFUSION THROUGH MYOGLOBIN [J].
ELBER, R ;
KARPLUS, M .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1990, 112 (25) :9161-9175