Single subunits

Figure 5.9 The six four-stranded motifs in a single subunit of neuraminidase form the six blades of a propeller-like structure. A schematic diagram of the subunit structure shows the propeller viewed from its side (a). An idealized propeller structure viewed from the side to highlight the position of the active site is shown in (b). The loop regions that connect the motifs (red in b) in combination with the loops that connect strands 2 and 3 within the motifs (green in b) form a wide funnel-shaped active site pocket, [(a) Adapted from P. Colman et ah, Nature 326 358-363, 1987.]...

Figure 5.19 Schematic picture of a single subunit of influenza virus hemagglutinin. The two polypeptide chains HAj and HA2 are held together by disulfide bridges.

Cluster Fx was also identified via its EPR spectral features in the RCI photosystem from green sulfur bacteria 31, 32) and the cluster binding motif was subsequently found in the gene sequence 34 ) of the (single) subunit of the homodimeric reaction center core (for a review, see 54, 55)). Whereas the same sequence motif is present in the RCI from heliobacteria (50), no EPR evidence for the presence of an iron-sulfur cluster related to Fx has been obtained. There are, however, indications from time-resolved optical spectroscopy for the involvement of an Fx-type center in electron transfer through the heliobacterial RC 56). 

Figure 5.6 A simple icosahedral virus. Each face has three subunits. A single subunit consists of one or more proteins, (a) Whole virus particle, (b) Virus particle opened up nucleic acid released.

Figure 6.3 Structure of recombinant HoLF (a) a half shell showing the relative positions and interfaces between symmetry-related subunits (b) schematic diagram indicating labelling used for symmetry-related subunits (c) detail of a single subunit. From Hempstead et al., 1997. Reproduced by permission of Academic Press.

However, since SMCC forms nonreversible thioether linkages with sulfhydryl groups, it only can be used in the preparation of immunotoxins if intact A-B toxins are employed in the conjugate. In such conjugates, the A chain still have the potential for reductive release from the B-chain subunit after cellular docking and internalization. Immunotoxins prepared with A-chain or single-subunit toxins will not display cytotoxicity if crosslinked with SMCC, since the crosslinker does not create cleavable disulfide bonds upon conjugation. 

To construct a spherical shell using a single subunit, n= 1, the only structure obtainable is S. As outlined above, it is impossible to construct a spherical molecular host using a single chemical entity, and therefore S does not represent a self-assembled spherical framework. 

HIF-lyS, is CBC. As shorthand, cullin-containing E3s are often referred to as multi-subunit E3s to underscore the need for multiple subunits for discernable activity. This is clearly an over-simplification, as single subunit, non-cullin, E3s can also function in the context of more complex assemblies. For more detail on cullin-containing E3s see Chapters 6 and 7. 

Note that the sum over i is over all four states of a single subunit. The unit vectors (LI I and (HI I are constants. When Eq. (7.4.24) reduce to... 

Figure 8.14. (a) A schematic multisubunit enzyme. Each subunit contains one catalytic (A) and one regulatory (R) site. The subunits ate arranged cyclically, i.e., them + 1 subunit is the same as the first, (b) A single subunit in the two conformational states L and H. 

A molecular structural property wherein a rotation of 180° leads to the same superimposable structure. Because proteins are made up of L-amino acid residues, neither a single subunit nor a multisubunit protein can possess a plane or point of symmetry. However, proteins do exhibit dyad symmetry. This structural property allows many DNA-binding proteins to make equivalent contacts to the two antiparallel chains of the nucleic acid. 

In simple cases, the CRU involves a single subunit. In more complex cases, it is often necessary to draw a large segment of the polymer chain, for example,... 

The CRU in a polymer chain may contain one or more subunits. A simple CRU is one that can be described by single subunit. A complex CRU has at least two subunits. 

MNNG N-methyl-N -nitro-N-nitrosoguanidine. monomer single subunit of a compound such as a protein, monomorphic with one form. 

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