Metabolic network modularity in archaea depends on growth conditions

Network modularity is an important structural feature in metabolic networks. A previous study suggested that the variability in natural habitat promotes metabolic network modularity in bacteria. However, since many factors influence the structure of the metabolic network, this phenomenon might be limited and there may be other explanations for the change in metabolic network modularity. Therefore, we focus on archaea because they belong to another domain of prokaryotes and show variability in growth conditions (e.g., trophic requirement and optimal growth temperature), but not in habitats because of their specialized growth conditions (e.g., high growth temperature). The relationship between biological features and metabolic network modularity is examined in detail. We first show the absence of a relationship between network modularity and habitat variability in archaea, as archaeal habitats are more limited than bacterial habitats. Although this finding implies the need for further studies regarding the differences in network modularity, it does not contradict previous work. Further investigations reveal alternative explanations. Specifically, growth conditions, trophic requirement, and optimal growth temperature, in particular, affect metabolic network modularity. We have discussed the mechanisms for the growth condition-dependant changes in network modularity. Our findings suggest different explanations for the changes in network modularity and provide new insights into adaptation and evolution in metabolic networks, despite several limitations of data analysis.     

Expression of the pregnancy-specific beta 1-glycoprotein genes in human testis

Northern blot analysis with placental pregnancy-specific beta 1-glycoprotein (SP1) cDNA probe showed the presence of SP1 mRNAs in human testis. Presence of translational products of the mRNAs was demonstrated by Western blot analysis with anti-human SP1 antibodies albeit difference in mobilities between the testis and placental proteins was apparent. Screening of human testis cDNA library with placental SP1 probe yielded 4 groups of positive clones. Two groups were identical to human placental SP1 cDNAs previously reported. The other 2 groups consisted of cDNA of incompletely processed mRNAs. These 2 groups were present in high abundance. Sequence analysis suggested that the cDNAs were products of different genes.