Cysteine binding

FIGURE 11.2 Common cysteine binding pattern for two interacting cubanes. 

The sequence His-Cys-His has an extended chain conformation. In this sequence, the cysteine binds type 1 and the two histidines, two separate copper atoms of the trinuclear cluster, thus making the shortest distance from the type 1 copper to the trinuclear cluster 13 A. Within the cluster, the Cu-Cu distances are 3.4, 3.9, and 4 A. It should be noted that none of the histidines bridges the copper atoms, unlike SOD, in which a histidine bridges the copper and zinc. The pattern of histidine binding to the trinuclear cluster is rather clever two His-X-His pairs from separate domains, His-Cys-His (507-509) and His-Gly-His (106-108), bind the... 

Figure 2 Active sites of hemocyanins from horseshoe crab L. polyphemus (a oxy b deoxy), spiny lobster Panulirus interruptus (c), sweet potato Ipomoea batatas (d), Octopus dofleini (e), Rapana thomasiana (f). Cleary the four alpha-helix bundle motif with the metal center can be seen. The three histidines coordinating Cu-A are colored red, those coordinating Cu-B green. The two copper atoms are colored blue and oxygen red. The cysteines binding covalently a histidine at the Cu-A site are colored yellow. In the case of Ipomoea, a water molecule connects the two copper atoms...

As seen from the amino-acid sequence for PsaC in Fig. 7 and that for the P. aerogenes ferredoxin in Fig. 9, cysteines 11, 14, 17 and 58 coordinate to FeS-B and cysteines 21, 48, 51 and 54 to FeS-A. The three-dimensional structure of the P. aerogenes ferredoxin may be utilized to show the cysteine coordination patterns for the two [4Fe 4S] clusters in the chloroplast PsaC subunit. Taking the two cysteine binding motifs. 

Nickel-cysteine binding supported by phosphine chelates... 

The half-life (x) of e-N-maleyl lysine is 11 h at pH 3.5 and 37 °C. More rapid cleavage is observed with the 2-methyl-maleyl derivative (x < 3 min at pH 3.5 and 20 °C) and the 2,2,3,3-tetrafluoro-succinyl derivative (x very low at pH 9.5 and 0°C). Cysteine binds maleic anhydride through an addition reaction. The S-succinyl derivative is quite stable. This side reaction is, however, avoided when protein derivatization is done with exo-cis-3,6-end-oxo-l,2,3,6- tetrahydrophthalic acid anhydride ... 

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