Koji Ohnishi

Cystatins of family II are harboring two domains which retain inhibitory activities against the proteinases

Two cyclic peptides, Ac-CTKSQPNLDTC-NH2 (SA-LOOP1) and Ac-CSFQIYEVPWE DRMSLVNSRC-NH2 (SA-LOOP2) were prepared. These sequences are respectively found in the second and third exons of cystatin SA and are well conserved among the cystatins of family II. In addition, these sequences are extremely homologous to the inhibitory regions of several serine-proteinase inhibitors. The peptides were assayed for their inhibiting properties towards serine- and cysteine-proteinases. SA-LOOP1 inhibited porcine pancreatic trypsin (Ki = 370 microM), but did not inhibit cysteine-proteinases. SA-LOOP2 inhibited not only porcine pancreatic alpha-chymotrypsin (Ki = 23 microM) but also papain (Ki = 24 microM) and ficin (Ki = 52 microM). These data indicate that the exon-intron organization of the cystatin genes coinside with the structural and/or functional domains of the protein, and may have significant implications for understanding the active sites of cystatins.

Long-lasting memory of sounds combined with reward in rats

We investigated the effects of sound stimuli combined with reward on the subsequent sound discrimination. Water-deprived rats were exposed to one of two sounds (S+ or S-) in a trial, and licking a spout only during the presentation of S+ was rewarded with water. The percentage of trials in which licking occurred was calculated separately for S+ and S-, and sound discrimination was estimated from the difference in the percentage. S+ and S- were significantly discriminated during an 8 h period. In the second test after 1-2 weeks, sound discrimination for the same S+ and S- was significantly better than that for the S+ of the previous S- and S- of the previous S+. These findings indicate that the memory of the sounds combined with reward in the first test was maintained for 1-2 weeks.

Domain structures and molecular evolution of class I and class II major histocompatibility gene complex (MHC) products deduced from amino acid and nucleotide sequence homologies

Domain structures of class I and class II MHC products were analyzed from a viewpoint of amino acid and nucleotide sequence homologies. Alignment statistics revealed that class I (transplantation) antigen H chains consist of four mutually homologous domains, and that class II (HLA-DR) antigen β and α chains are both composed of three mutually homologous ones. The N-terminal three and two domains of class I and class II (both β and α) gene products, respectively, all of which being ∼90 residues long, were concluded to be homologous to β2-microglobulin (β2M). The membraneembedded C-terminal shorter domains of these MHC products were also found to be homologous to one another and to the third domain of class I H chains. Class I H chains were found to be more closely related to class II α chains than to class II β chains. Based on these findings, an exon duplication history from a common ancestral gene encoding a β2M-like primodial protein of one-domain-length up to the contemporary MHC products was proposed.

Simultaneous cognitive origin of life and information

Shannon’s information quantity I(E) = log(1/P(E)) is defined under an assumption of the existence of a “cognitive subjective entity” capable of judging yes/no or occurred/not-occurred of an event E (which occurs with a probability P(E)). The final acceptor/user of information is a living individual, although first and/or intermediate sender(s) and/or acceptor(s) of information may be either living individual(s) or nonliving element(s) or man-made machine(s). Therefore we can conclude that information is a most essential character of living individuals, and that information and life must have emerged simultaneously as a “minimum cognitive system” (MCS). Since then, living individuals/lives must have evolved as “self-revising learning neural network machines” capable of “active evolution”. How MCS could have emerged was discussed.

Origin of the word-initial consonant system of the Japanese-Ryukyuan (JR) language from the Oceanic consonant system: elucidation by JR-Oceanic consonant correspondence laws

Proto-Japanese-Ryukyuan (pJR) word-initial consonants were found to regularly correspond to Malayo-Polynesian (MP)/Oceanic (OC) consonants. An almost complete list of the correspondence laws were obtained based on a cognate list of (p)JR and MP/OC. The New Caledonian group shows a close similarity in cognate comparisons with pJR.

Towards a brief proof of the Four-Color Theorem without using a computer: theorems to be used for proving the Four-Color Theorem

In order to prove the Four-Color Theorem (FCT) without using a computer, some basic definitions and theorems which will be useful for proving the FCT are presented, and a bird’s-eye view of a brief proof is described and discussed. A complete proof will appear in the near future.

Sound-correspondence laws of word-initial consonants between proto-Indo-European and Austronesian languages

A macrocomparative analysis of the consonant systems of Indo-European (IE) and Austronesian (AN) language families elucidated 43 word-initial consonant-correspondence laws between proto-IE (pIE) and AN (proto-AN (pAN), proto-Malayo-Polynesian (pMP), MP, Oceanic (OC), etc.). pIE was concluded to have emerged from an eastern MP (E.MP) language closely akin to Bali-Sasak languages. Characteristic features in the emergence of new consonants from pre-existing consonant systems have been elucidated.

Comparative anatomy of group I introns and related RNA's

Group I intron is a typical class of ribozyme, whose origin is, however, unknown. The 407-base-long group I intron in the Tetrahymena cosmopolitanis 26S rRNA gene (GenBank Locus TCRRN) was compared with those RNAs compiled in Genbank Database. RNAs and RNA genes possibly homologous to group I introns were searched for from GenBank DNA D_a_r_~base by .employing Genentyx Software for homology search (I_/pman and Pearsons method). Based on the regions found to be possibly homologous to tRNAs and 5S rRNAs, the 407-base intron was roughly divided into four domains: domain I (bases I108), domain II (bases 110-225), domain Ill (approximately 238-351), and

Evolutionary Meanings of the Primary and Secondary Structures of the “UR-RNA”, A Primitive Possibly Self-Replicating Ribo-Organism Commonly Ancestral to tRNAs, 5S-rRNA and Virusoids

Recent advances in the study of catalytic RNAs have allowed us to consider that the first self-replicating organism was almost undoubtedly an RNA without protein-encoding informations (Watson et al., 1987; Orgel, 1987; Schwartz et al., 1987; Cech, 1989a; Joice, 1989). The class I intron of Tetrahymena pre-rRNA, virusoids, viroids, RNA portion (M1 RNA) of ribonuclease P and the delta element of hepatitis B virus are representatives of these catalytic RNAs (See reviews in Cech, 1989b and Diener, 1987a).

Towards a classification ofE.coli ribosomal proteins: A hypothetical ‘small ribosome’ as a primitive protein-synthesizing apparatus

Homologies were searched among the published primary sequences of 51E.coli ribosomal proteins, partly by ‘eye’ and partly by computer-assisted methods. By employing Moore and Goodmans alignment statistics for evaluating homology levels, 33 out of these 51 ribosomal proteins has been classified into 9 homology groups, some of which being yet tentative and remaining to be further analyzed. Taking it into consideration that most ribosomal protein genes are clustered atstr-stc region,rif region and several other regions, these results strongly suggest that most or all of the contemporary ribosomal proteins must have evolved by repeated gene duplications ofveryfew (oronlyone) primitive ancestral ribosomal protein gene(s). Thus it is most reasonable to propose that a ‘smallribosome’ consisting of very few (or only one) ribosomal protein(s) must have existed as a primitive protein-synthesizing apparatus.