: A : Q 946. N 2+ 3 H 2Ω , Pa 2N H Jou rnal of X iam en U n iversity (N atu ral Science) M ar. 2001

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1 40 2 ( ) V o l. 40 N o Jou rnal of X iam en U n iversity (N atu ral Science) M ar : (2001) , 1, 2, 1, 3, 1, 3 (1., 2., ) :,. (FeM o2co)m ofe7s9 (R 2 ),, FeM o2co ; N 2, C 2H 2 CO ;,.. : ; ; ; ; ; ; ; : Q 946 : A, (N 2) (N H 3),,,. 2. 4, 65%, 25%.. N 2+ 8 e H M ga T P, 2 N H H AD P+ 16 PO 2-4 Fe N 2+ 3 H 2Ω Ω , Pa 2N H 3 60, R ees X, FeM o2co ( )M ofe7s9 (R 2 ) [ 1, 2 ].,M o, 3 Λ32,. Α2 Α2 : : ( ); ; :, (1964- ),, ; (1914- ),,. 3 ; e2m ail: k rtsai@xm u. edu. cn

2 2 : [1, 2 ] F ig. 1 Experim ental coo rdination structure of iron mo lybdenum cofacto r ( FeM o2co ) in nitrogenase [1, 2 ], Α2 Α2, 1 1, 1. 1, FeM o2co N 2. FeM o2co N 2,., [ 3 9 ]., FeM o2co N 2, 2 4. N 2 FeM o2co : N 2 FeM o2co ; N 2 FeM o2co (N 2 FeM o2co ) ;, 2. 2 ( ) EXA FS FeV FeM o [ 10 ], (H 4cit= C 6H 8O 7) Fe V M o. R, R 2 Α2 Α2 Β Χ2 ; ( : K lebsiella p neum on iae) M ofe7s9 ( ),,., [ 11 ].,,,M oo 2-4 VO 3-4 ( ) N if B FeM o2co, FeM o2co [ ] ( 3).,. ( ) ( ), ( ) ( ) ( ) ( ), (V ) ( 4) [ 13 ],,M IT [ 14 ]. Α2 Α2., FeM o2co.,, (V )

3 ( ) F ig. 2 D ifferent models of the active site of N 2 in iron2mo lybdenum cofacto r of nitrogenase. V 2O 2, Α2 Α2 V, Β2,. ( 5). 3 (V ), Β2 F ig. 3 B io synthesis of iron mo lybdenum cofacto r

4 2 : (V ) K2 [VO 2 (C 6H 6O 7) ]2 4H 2O F ig. 4 A nion structure of po tassium dioxocitrato vanadate ( V ) K2 [VO 2 (C 6H 6O 7) ]2 4H 2O 5 (V ) N a2k2 [VO 2 (C 6H 5O 7) ]2 9H 2O F ig. 5 Po lym eric anion structure of po tassium sodium dioxohydrogencitrato vanadate (V ) N a2k2 [VO 2 (C 6H 5O 7) ]2 9H 2O, (V ) [ ]. [ 11, 21 ], ( ). (V ), ( IV ) ( 6). Α2 Α2 Β2, Α2 6 ( IV ) N a4 V 2O 2 [ ], [ 15, 25 ]. [VO (C 6H 4O 7) ]2 6H 2O F ig. B ino ( IV ) 6 A nion structure of sodium oxocitrato ( IV ) [ 26 ], vanadate ( IV ) N a4 ( IV ) (H neo) 3 [ (VO ) 2 (cit) (H cit) ] [VO (C 6H 4O 7 ) ]2 4H 2O, ( IV ), 6H 2O.,O rm e2john son (V ) [K 2 (H 2O ) 5 ] [ (VO 2) 2 (R, S 2hom ocitrate) 2 ] H 2O [ 27 ], (V ), (V ), R 2 S ( ), R 2, ph 3 9,

5 ( ) , ph,., ph (7 8), Α2 Α2 Β2,, Β2, [ (3) nm ]., Α2 Α2,. (V I)., (V I), ( 7) [ 28 ] : 7 F ig. 7 Po ssible pathw ay of mo lybdenum transfer in nitrogenase FeM o2co, Α2C. ph 5 6, [ (M oo 2) 2O (cit) 2 ] 6-,, Α2 Α2 Β2,., [ (M oo 2) 2O (H cit) 2 ] 4-, [M oo 2 (H 2cit) 2 ] 2- ( 8) [ ]. 2. 3, R 2 S 2, S 2 (V I) (V I) 2S + 2S,, (V I) (V I) +, 1 M o (W ) 2O. 1, + ;. :, + ; R 2, R 2 + 2R 2R., ( 9) :

6 2 : F ig. 8 Syntheses and transfo rm ation of monom eric and dim eric citratomo lybdates 1 M o (W ) 2O T ab. 1 Comparisons of M o (W ) 2O distances ( 10-1 nm ) and our assignm ent of abso lute configuration in citrato and m alato comp lexes (H 4cit= citric acid) Com p lex M 2O (alkoxy) M 2O (Α2carboxy) Configu ration assignm ent N a2 [M oo 2 (H 2cit) 2 ] 3H 2O (6), (7) (7), (6) g+ 32 N a2 [WO 2 (H 2cit) 2 ] 3H 2O (6), (7) (8), (7) g+ 32 (N H 4) 4 [M o 4O 11 (m al) 2 ] 6H 2O ,, +, + 2S, S 33 (N H 4) 4 [M o 4O 11 (m al) 2 ] H 2O (15) (15),,, 2S, S 34, 35 (N H 4) 4 [M o 4O 11 (m al) 2 ] 6H 2O (6) (6),, +, + 2R, R 36 C s2 [M oo 2 (Hm al) 2 ] H 2O (8) (9) 2S 37 N a3 [WO 2H (S 2m al) 2 ] (4) (4) + 2S 38 reḟ, 70. N 2 C 2H 2 D 2O

7 ( ) F ig. 9 Po ssible bio synthesis pathw ay of iron mo lybdenum cofacto r in nitrogenase transgcis2c 2H 2D 2, FeM o2co, 3 Λ2S H 2S,N N HC CH ( ) [2Fe ], [M o, 3Fe, 3Fe ] [ 3Fe, 3Fe ],,, [2Fe ].,,N N CH 2 (HC= CH ), CH 2 (N = N ) > HC CH > CH 3N C> > CH 3C CH > CH 3C= N, HC CH H 2C= CH 2, D 2O C 2H 2D 299% [ 6, 7, ]. CO,,,N 2, CO [ 11 ]., P M.

8 2 : 327,,, P M, Χ2 O, HOH, H + Cys Α62 2HN 2Gly Α61 O, O H is Α442 N [M o ]., Β2 O, HOH, Cys Α62 2HN 2Gly Α61 O ; O H is Α195 N Ε.,. : [ 1 ] K im J S, R ees D C. Structural models fo r the m etal centers in the nitrogenase mo lybdenum 2iron p ro tein[j ]. Science, 1992, 257: [ 2 ] How ard J B, R ees D C. Structural basis of bio logical nitrogen fixation [J ]. Chem. R ev., 1996, 96: [3 ] O rm e2johnson W H. N itrogenase structure: W here to now? [J ]. Science, 1992, 257: [ 4 ] Sellm ann D, U tz J, B lum N. O n the function of nitrogenase FeM o cofacto rs and competitive catalysts: chem ical p rincip les, structural blue2p rints, and the relevance of iron2sulfur comp lexes fo r N 2 fixation [J ]. Coo rd. Chem. R ev., 1999, : [5 ] Chan M K, K im J S, R ees D C. T he nitrogenase FeM o2cofacto r and P2cluster pair22. 2 reso lution structu res[j ]. Science, 1993, 260: [ 6 ] T sai K R, W an H L. O n the structure2function relationsh ip of nitrogenase M 2cluster and P2cluster pairs[j ]. J. C lu ster Sci., 1995, 6: [7 ],,,. M 2 P2 [J ]. ( ), 1996, 35: [8 ],. [J ]., 1995, 40: [9 ] L eigh A J. A fixation w ith fixation [J ]. Science, 1995, 268: [10 ] Eady R R, Structure2function relationsh ip s of alternative nitrogenases[j ]. Chem. R ev., 1996, 96, [11 ] Gra β nberg K L C, Go rm al C A, D urrant M C, et al. W hy R 2Homocitrate is essential to the reactivity of FeM o2cofacto r of nitrogenase: studies on N if V - extracted FeM o2cofacto r [J ]. J. Am. Chem. Soc., 1998, 120: [ 12 ] M ller A, K rahn E. O n the synthesis of the FeM o cofacto r of nitrogenase: Gene2contro lled in nature versu s labo rato ry2p roduced by m an [J ]. A ngew. Chem. Ind. Ed. Engl., 1995, 34: [ 13 ] Zhou Z H, Yan W B, W an H L, et al. M etal2hydroxycarboxylate interactions: syntheses and structures of K2 [VO 2 (C 6H 6O 7 ) ]2 4H 2O and (N H 4 ) 2 [VO 2 (C 6H 6O 7 ) ]2 2H 2O [J ]. J. Chem. C rystallogṙ, 1995, 25: [ 14 ] W righ t D W, H um iston P A, O rm e2johnson W H, et al. A unique coo rdination mode fo r citrate and a transition m etal: K2 [VO 2 (C 6H 6O 7) ]2 4H 2O [J ]. Ino rg. Chem., 1995, 34: [ 15 ] Zhou Z H, W an H L, H u S Z, et al. Syntheses and structures of po tassium 2ammonium dioxocitratovanadate(v ) and sodium oxocitratovanadate ( IV ) dim ers[j ]. Ino rg. Ch im. A cta, 1995, 237: [16 ] Zhou Z H, Zhang H T, H uang T S. Syntheses and characterization of citrato comp lexes of vanadium [J ]. J. M o l. Sci., 1995, 11: [ 17 ] Zhou Z H, W an H L, T sai K R. Synthesis and crystal structure of sodium ammonium dim eric

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10 2 : 329 structure of tetraammonium aa 2Λ2oxobis {[ gied 2Λ32( S ) 2m alato2o 1, O 2, O 4, O 4 ]2di2Λ2oxobis [ dioxom o lybdate (V I) ]} m onohydrate[j ]. Z. K ristallogṙ, 1977, 145, [36 ] Zhou Z H, Yan W B, W an H L, et al. Comp lexation of mo lybdenum (V I) w ith R 2 and S 2m alic acid, the crystal structure of (N H 4) 4 [ (M oo 2) 4O 3 (R 2m al) 2 ] 6H 2O [J ]. Ch inese J. Strucṫ Chem. 1995, 14, [37 ] Knobler C B, W ilson A J, H ider R N, et al. M o lybdenum (V I) comp lex w ith m alic acid: their inter2 relationsh ip s, and the crystal structure of dicaesium bis [ (S ) 2m alato (22) ]2cis2dioxomo lybdate (V I) 2 w ater (1g1) [J ]. J. Chem. Soc. D alton T ran ṡ 1983, [38 ] Zhou Z H, W ang G F, Hou S Y, et al. T ungsten2m alate interaction. Synthesis, spectro scop ic and structural studies of homoch iral S2m alato tungstate (V I), + 2N a3 [WO 2H (S 2m al) 2 ] [J ]. Ino rg. Ch im. A cta, 2001, 314: [39 ] Q iu X H, Dong E H, Zhou Z H, et al. T he effects of citrato mo lybdate on the grow th rate of A zo tobacter V inelandii[j ]. Chem. J. Ch inese U n iv. (Spp l), 2000, 12: 152. [40 ] Zhang F Z, H uang J W, H uang H Q, et al. T he binding site of N 2 and N 2O in nitrogenase indirectly detected by the change of transgcis of DHC= CHD in p roducts[j ]. A cta B iophy. Sinica, 1999, 15: 1-8. [ 41 ],,,. [J ]., 1999, 15: [42 ],,. 1 H NM R [J ]., 1999, 57: [43 ],,,. N 2 N 2O [J ]. ( ), 1999, 38 (4): Catalytic M echan ism of N itrogen R eduction by N itrogenase and its Chem icalm odeling ZHOU Zhao2hu i 1, YAN W en2b in 1, ZHAN G Feng2zhang 2, W AN H u i2l in 1, T SA I Kh i2ru i 1 (1. D ep ṫ of Chem., 2. D ep ṫ of B io l., X iam en U n iv., X iam en , Ch ina) Abstract: N it rogena se ca ta lyzes the reduct ion of d in it rogen to amm on ia coup led to the hydro lysis of A T P, w h ich is cen tral to the p rocess of b io logical n itrogen fixation. X2ray crystallograph ic structu res has revealed its catalytic m etal cen ter FeM o2cofacto r as a cage structu re of M ofe7s9 (R 2hom ocitrate), in w h ich the hom ocitrate coo rdinate b iden tately to m o lybdenum. R ecen t effo rts tow ards estab lish ing the m echan ism of activation of n itrogen around the m etal cen ter and the early b io syn thesis p rocess of FeM o2co are review ed, w h ich reflect a com b ination of structu ral, spectro scop ic, syn thetic, b iochem ical and theo retical app roaches to th is challenging p rob lem pursued especially from the n itrogen fixation group of X iam en U n iversity. Key words: n it rogena se; iron2m o lybdenum cofacto r; iron2vanad ium cofacto r; chem ica l m odeling; hom ocitric acid; citric acid; ch iral; configu ration assignm en t