Mammalian biological roles

The high-mobility group proteins were initially characterised as prominent components of chromatin [1,17] each mammalian nucleus contains, on average, approximately 10 -10 HMGBl molecules [16,63]. This abundance implies a major chromatin-related function but the precise biological role of the proteins has proved elusive. 

Following the demonstration that nitric oxide (NO) has many important roles in mammalian biology, a veritable avalanche of reports of reactions of NO with a... 

NO plays an important role in mammalian biology, including functions in the cardiovascular system, neurotransmission, and the immune response [73-79]. The reactive NO species (RNOS), which are generated, transferred, and consumed within biological and medical processes, may be viewed as NO, NO , and NO+ species. The release of the active forms of NO from the NO donor drug may proceed on spontaneous, enzyme-catalyzed, or light-induced pathways. 

A mammalian cell may contain as few as 2000 different proteins and as many as 50,000 at any given time. Each of these is uniquely suited to the function it performs, and this in turn depends on its size, shape, solubility in aqueous media, acid-base properties, propensity to form fibers, and numerous other physical and chemical properties. The component amino acids are largely responsible for the ability of proteins to perform their biologic roles. The properties of amino acids are therefore of paramount importance in determining how proteins work. 

The hypoxic response plays an important role in mammalian biology (122), and alterations in tissue oxygenation are hallmarks of many human diseases including stroke, heart disease, vascular disease, and cancer (123). Across a range of cancers, observed associations between aggressive phenotypes and micro-environmental hypoxia have focused attention on the molecular dissection of hypoxia pathways (124). 

The name cytochrome bs is now generally used for a protohemoprotein which exists in high amounts in the endoplasmic reticulum of mammalian liver cells. It shows an asymmetrical a-absorption band with a peak at 556 nm and a shoulder around 560 nm in the reduced state. However, there has been some confusion about its nomenclature. This cytochrome is firmly bound to the membrane structure and reduced with NADH by a flavoprotein (cytochrome bs reductase) which is also bound to the membrane. It is solubilized by proteolytic cleavage from the membrane and has been crystallized from several sources. The molecular weight of such preparations are about 11,000. Although both primary and ternary structures of such preparations are known, its biological role is still uncertain. Earlier findings have been fully reviewed by Strittmatter (94)-... 

Demple B, Sung JS (2005) Molecular and biological roles of Apel protein in mammalian base excision repair. DNA Repair (Amst) 4 1442-1449 Dienel GA (1984) Regional accumulation of calcium in postischemic rat brain. J Neurochem 43 913-925... 

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