Cysteine, Cys

Fig. 1. Model of a ligand gated ion channel (LGIC) where (a) is the structure of a generic LGIC subunit showing the two cysteine (Cys) residues common to all LGIC subunits, and (b) shows the arrangement of five such subunits as a pentamer having psuedo-cyclic symmetry delineating a gated, fluid-filled...

The structures of all three types of enzyme have been recently resolved 417-421 The first was the structure of the [NiFe] enzyme from Desulfovibrio gigas422 which revealed an active site containing a Ni center coordinated by 7-S of a cysteine (Cys 530) in an apical position and by three... 

Copolymers of a-hydroxy acids and a-amino acids are one type of poly(ester-amide)s and are called polydepsipeptides (PDPs) [17]. Since some of natural occurring a-amino acids, typically Asp, Glu, lysine (Lys), cysteine (Cys), serine (Ser), and threonine (Thr), possess reactive (hydrophilic) side-chain groups, PDPs... 

Activation parameters A 77, AS and A I7 have been determined for all nine combinations of [Pd(LLL)(H20)]2+, LLL = dien, terpy, or bis(2-pyri-dylmethyl)amine reacting with L-cysteine (cys), DL-penicillamine (pen), or glutathione (glu) (250). All AS and A I7 values are negative, consistent with associative activation, but there is no AS /A l7 correlation, except for the three reactions with pen. Indeed all the reactions with... 

The crystal structure (Strop et al. 2001) reveals a homodimer with the zinc atom ligated by the sulfur atoms of two cysteines (Cys 32 and Cys 90) and the nitrogen atom of a histidine (His 87), as is the case for the plant-type enzyme (Fig. 11.3). The active site contains an HEPES buffer molecule in a position that implicates involvement of Asp 34 in the transport of protons after ionization of the zinc-bound water. 

The ability of coordinated NO to react with thiols has led to the suggestion of an alternative mechanism for activating guanylate cyclase. This involves nitroprusside oxidation of protein sulfhydryls to cross-link the protein with a disulfide bridge. For example, papain, which has an essential cysteine (cys-25) and glyceradehyde-3-phosphate dehydrogenase (cys-149) are both inhibited by nitroprusside with formation of [Fe(CN)5(NO)] and [Fe(CN)4NO] [132]. The suggested anaerobic reaction is ... 

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