Low Molecular Weight subunits

High-molecular-weight complex peptidases composed of a series of low-molecular-weight subunits are found in the cytosol [27], These enzymes were... 

Spectroscopic and crystallographic studies have identified four Fe S clusters in the membrane-bound photosynthetic electron transport chain of plant and cyanobacterial chloro-plasts. One is the Rieske-type [2Fe-2S] + + center in the cyt b(,f complex, which catalyzes electron transfer from plasto-quinol to plastocyanin with concomitant proton translocation, and is functionally analogous to the cyt bc complex, with cyt / in place of cyt The remainder are low-potential [4Fe 4S] + + centers in Photosystem I which constitute the terminal part of the electron transfer chain that is initiated by the primary donor chlorophyll. One is a very low-potential [4Fe S] + + center, Fx (Em =-705 mV), that bridges two similar subunits (PsaA and PsaB) and is coordinated by two cysteines from each subunit in a C-Xg-C arrangement. This cluster transfers electrons to the 2Fe-Fd acceptor via an electron transfer chain composed of Fa, a [4Fe S] + + cluster with Em = -530 mV, and Fb, a [4Fe S] + + clusters with Em = -580 mV. Fa and Fb are in a low-molecular weight subunit (PsaC, 9 kDa) that shows strong sequence and structural homology with bacterial 8Fe-Fds. The center-to-center distance between Fx and Fa and between Fa and Fb are 14.9 A and 12.3 A, respectively, well... 

Murata, K., T. Sasaki, S. Yasumasu, I. Iuchi, J. Enami, I. Yasumasu and K. Yamagami. Cloning of cDNAs for the precursor proteins of low-molecular-weight subunit of the inner layer of the egg envelope (chorion) of the fish Oryzias latipes. Dev. Biol. 167 9-17, 1995. 

Carboxypeptidase N is synthesized in the liver [103] and circulates as a 280,000 Mr tetrameric complex. It is composed of two identical high molecular weight subunits (Mr 83,000), which are heavily glycosylated and lack enzymatic activity, and two identical low molecular weight subunits (Mr 55,000), which contain the active center [104,105]. 

Hodo, H. G., and Blatti, S. P., 1977, Purification using polyethyleneimine precipitation and low molecular weight subunit analyses of calf thymus and wheat germ DNA-dependent RNA polymerase II, Biochemistry 16 2334-2343. 

P-Gal has a molecular weight of 540,000 and is composed of four identical subunits of MW 135,000, each with an independent active site (Melchers and Messer, 1973). The enzyme has divalent metals as cofactors, with chelated Mg+2 ions required to maintain active site conformation. The presence of NaCl or dilute solutions (5 percent) of low-molecular-weight alcohols (methanol, ethanol, etc.) causes enhanced substrate turnover. P-Gal contains numerous sulfhy-dryl groups and is glycosylated. 

In addition to the classification of liquid chromatographic enantioseparation methods by technical description, these methods could further be classified according to the chemical structure of the diverse CSPs. The chiral selector moiety varies from large molecules, based on natural or synthetic polymers in which the chirality may be based on chiral subunits (monomers) or intrinsically on the total structure (e.g., helicity or chiral cavity), to low molecular weight molecules which are irreversibly and/or covalently bound to a rigid hard matrix, most often silica gel. 

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