Molecular biology of complement

Complementary DNA clones corresponding to most of the proteins of a major amplification and effector of immune host defenses, the complement system, have been isolated and characterized. Availability of these molecular probes has substantially increased our information about and understanding of the structure of the complement proteins and regulation of complement gene expression. Information about the proteins has led to the generation of potential pharmacological agents for the selective control of inflammation. Understanding of the regulatory mechanism has provided insights into the mechanisms accounting for the response to several cytokines including interferon-gamma, interleukin-1 and tumor necrosis factor. Finally, complement molecular genetics has been stimulated so that the basis for several complement deficiency disorders has been elucidated.     

Molecular biology of proteasomes

Eukaryotic proteasomes are unusually large proteins with a heterogeneous subunit composition and have been classified into two isoforms with apparently distinct sedimentation coefficients of 20S and 26S. The 20S proteasome is composed of a set of small subunits with molecular masses of 21–32 kDa. The 26S proteasome is a multi-molecular assembly, consisting of a central 20S proteasome and two terminal subsets of multiple subunits of 28–112 kDa attached to the central part in opposite orientations. The primary structures of all the subunits of mammalian and yeast 20S proteasomes have been deduced from the nucleotide sequences of cDNAs or genes isolated by recombinant DNA techniques. These genes constitute a unique multi-gene family encoding homologous polypeptides that have been conserved during evolution. In contrast, little is yet known about the terminal structures of the 26S proteasome, but the cDNA clonings of those of humans are currently in progress. In this review, I summarize available information of the structural features on eukaryotic 20S and 26S proteasomes which has been clarified by molecular-biological methods.     

Molecular biology of archaebacteria

In the process of phylogenetic studies, based on the comparative analysis of sequences of 16S (18S) rRNA, C. Woese and collaborators discovered that some microorganisms, which previously had been described as bacteria, form a group named archaebacteria, differing from other bacteria as well as from eukaryotes to the same extent as the latter differ from each other. A review of the work leading to that result, as well as characteristics of archaebacteria with emphasis on their biochemistry and molecular biology, is presented.     

Molecular biology of photosynthesis

Book reviews

Molecular biology of photosynthesisGovindjee, H.J. Bohnert, W. Bottomley, D.A. Bryant, J.E. Mullet, W.L. Ogren, H. Pakrasi, and C.R. Somerville (Eds.), Dordrecht: Kluwer Academic Publishers, 1989. xxvii + 815 pages. £130.00. ISBN 0-7923-0097-1     

Molecular biology of Leishmania

Leishmania is a trypanosomatid protozoa with a digenetic life cycle. Sandflies inject promastigotes, the free living form present in their salivary glands, into mammals where the parasite colonizes macrophages, transforming into intracellular amastigotes. The cycle is completed when during a blood meal the insect ingests infected macrophages, the amastigotes are released in the gut where they transform back into promastigotes. Leishmania has to adapt to the changing life conditions, from free-living forms in the poikilothermic insect vector to obligatory intracellular parasite in the homeothermic mammalian host. It also has to adapt to the acidic pH of the macrophage's phagolysosome where amastigotes multiply. The adaptative response of Leishmania includes morphological, physiological, and biochemical changes. Promastigotes can be grown in culture medium. Studies of changes taking place during adaptation have been facilitated by the establishment of in vitro conditions that allow the transformation of amastigotes into promastigotes and vice versa. The system is well suited for studying regulation of gene expression during adaptative differentiation. Some mechanisms of mRNA processing are unique to these protozoa: trans-splicing and RNA editing. Several genes that are differentially expressed in the two stages have been studied. No obvious cis regulatory motifs have been found in the DNA.     

Molecular biology of CLL

Recently, major advances have occurred in our understanding of the biology of chronic lymphocytic leukemia (CLL). CD5-positive CLL cells were once assumed to originate from immature, immunologically incompetent B lymphocytes, and to passively accumulate due to increased life time. In 1999, two research groups demonstrated that CLL, which is a morphologically uniform but clinically heterogenous disease, can be classified into two major subgroups on the basis of the mutational status of the immunoglobulin heavy chain (IgH) genes. It was also suggested that these two groups both originate from mature cells that have passed the antigen selection process. This hypothesis was confirmed by gene expression studies indicating a uniform pattern characteristic to memory cells, as well as specific B-cell receptor (BCR) structures supporting the existence of a functional antigen selection. The differences in the BCR signal transduction mechanisms may underlie the different clinical behavior in which zeta-associated tyrosine kinase (ZAP-70) may play a pivotal role, since elevated ZAP-70 expression is likely to be an unfavorable prognostic factor in CLL. The diagnostic testing for ZAP-70 expression plays an important role in the therapeutic decisions.     

Molecular biology of mosses

Plant Molecular Biology -     

Molecular biology in physiology

The aim of this symposium on molecular biology in physiology was to introduce molecular biology to physiologists who had relatively little exposure to the new developments in this field, so that they can become conversant on this topic and contribute to the advancement of physiology by incorporating molecular biological approaches as a part of their research arsenal. After the discussion of the basic concepts, terminology, and methodology used in molecular biology, it was shown how these basic principles have been applied to the study of the genes encoding two membrane proteins that have important transport functions (band 3 and ATPase). The second half of the symposium consisted of papers on the state-of-the-art developments in the application of molecular biology to the studies of the atrial natriuretic factor and renin genes, adenylate cyclase-coupled adrenergic receptors, acetylcholine receptors and sodium channel, and long-term and short-term memories. The ultimate goal is that these examples will provide an impetus for the opening of new frontiers of research in physiology by taking advantage of the tools developed from recent advances in molecular biology.