Receptor-binding affinities of human epidermal growth factor variants having unnatural amino acid residues in position 23

Ile-23 of human epidermal growth factor (hEGF) has been indicated, by mutagenesis and NMR studies, to be directly recognized by the receptor. In the present study, an unnatural phenylalanine analog, either 2-azaphenylalanine (2aF), 3-azaphenylalanine (3aF), 4-azaphenylalanine (4aF), or 4-fluorophenylalanine (4fF), was incorporated by an in vivo protein synthesis system into position 23 of [Phe23]hEGF, which retains appreciable receptor-binding affinity (about 20% of the wild type). We compared the receptor-binding affinities of the variants with that of [Phe23]hEGF and found that substitution of Phe-23 with 2aF or 3aF raised the affinity, while substitution with 4aF or 4fF remarkably reduced the affinity. The tertiary structure of [Phe23]hEGF was not significantly affected by the substitution of Phe-23 with 2aF, as shown by the two-dimensional nuclear magnetic resonance analysis. In addition, the substitution of residue 23 with His or Tyr produced an hEGF variant with a slightly higher receptor-binding affinity than that of [Phe23]hEGF. Our results suggest that the receptor has an asymmetric hydrophobic pocket for recognition of the side chain in position 23 of hEGF. Furthermore, on the receptor surface, this pocket seems to be adjacent to a less hydrophobic region with a hydrogen-bond acceptor and donor. Thus, the use of unnatural amino acids in addition to the 20 natural ones allows analyses of the structure-function relationship of a protein at a higher resolution than conventional site-directed substitution by only natural amino acid residues.

Combined effects of magnesium deficiency and an atherogenic level of low density lipoprotein on uptake and metabolism of low density lipoprotein by cultured human endothelial cells. I. Biochemical data

The effects of magnesium deficiency on uptake and metabolism of low density lipoprotein (LDL) were investigated using human arterial endothelial cells cultured in media containing various concentrations of magnesium (100-1000 microM) and a high concentration of LDL (2 mg LDL cholesterol/ml) labelled with [3H]cholesteryl linoleate. The LDL uptake was time-dependent and increased for up to 8 h in both the magnesium-deficient and magnesium-sufficient treatments. The extent of LDL uptake progressively increased with the decrease in magnesium concentration of the medium. Surface-bound LDL also increased in a similar manner during the incubation but less extensively than the LDL uptake. The majority of radioactivity from internalized LDL was detected in unesterified cholesterol at all time points in both the magnesium deficiency and sufficiency groups. Only small amounts of radioactivity were found in cholesteryl esters. These findings indicate that most LDL taken up by the cells was rapidly hydrolysed but not readily re-esterified. The lack of re-esterification may be due to a relative deficiency of acyl-CoA:cholesterol acyltransferase (ACAT) and the presence of large amounts of unesterified cholesterol.

Combined effects of magnesium deficiency and an atherogenic level of low density lipoprotein on uptake and metabolism of low density lipoprotein by cultured human endothelial cells. II. Electron microscopic data

The effects of magnesium deficiency on low density lipoprotein (LDL) transport by cultured endothelial cells with a high concentration of LDL (2 mg of LDL cholesterol/ml) were investigated by electron microscopy and by counting the radioactivity of [3H]-LDL transported across an endothelial monolayer grown on culture plate inserts. Electron microscopic examination showed that the number of pits/vesicles in the apical side was time-dependently increased for 24 h in both magnesium-deficient and magnesium-sufficient groups with the exception of 1 h under magnesium sufficiency. The number of pits/vesicles in the basal side was also increased for 8 h in both groups, though there was a decrease at 24 h in the two groups. No difference between either magnesium group at the same time point was statistically significant. [3H]-LDL transport was also time-dependently increased in both magnesium-deficient and magnesium-sufficient groups. In contrast to the results obtained by electron microscopy, the amount of LDL transported under magnesium deficiency was much larger for 24 h than under magnesium sufficiency. Differences in LDL transport between magnesium groups were statistically significant at 4 and 8 h. This finding indicates that magnesium deficiency increases LDL transport across the endothelial monolayer. The increase may be due to energy-dependent movement across endothelial cells, energy-independent movement between cells, or both. However, we conclude that magnesium deficiency increases the energy-dependent LDL transport to some degree since intercellular gap formations were rarely observed in either magnesium group. This LDL transported to the subendothelial space may lead to LDL accumulation and initiate atherosclerosis.

Properties of human plasma lipid transfer protein in aqueous solution and at interfaces

Human plasma lipid transfer protein (cholesteryl ester transfer protein) has been characterized for its solution and surface properties. The protein is monomeric in aqueous solution up to 0.62 g/L (11.7 microM) as demonstrated by sedimentation equilibrium. It binds to the surface of a lipid microemulsion having an average diameter of 26 nm made from triolein and egg yolk phosphatidylcholine, with an estimated dissociation constant 1.2 x 10(-8) M, and the maximum saturation binding level is 8 protein molecules per particle regardless of the presence of apolipoprotein A-I. Circular dichroism measurement indicated that the protein in solution is predominantly in the beta-sheet/beta-turn conformation with some alpha-helix, and this profile does not undergo drastic change by its binding to the lipid surface. The analysis of the behavior of the protein in its monomolecular layer at the air-buffer interface indicated that it is also monomeric at the interface. LTP molecules occupied the same area per amino acid as other apolipoproteins in the monolayer but had a higher collapse pressure of its monolayer (18 dyn/cm), and the protein stayed at the interface even after the overcompressing monolayer far beyond the collapsing pressure up to 40 dyn/cm.

Site-specific incorporation of photofunctional nonnatural amino acids into a polypeptide through in vitro protein biosynthesis

Nonnatural amino acids with photofunctional groups were incorporated site-specifically into a polypeptide by using in vitro protein synthesizing system. The nonnatural amino acids were attached to tRNA(CCU) through chemical misacylation method, and added to the in vitro system with a mRNA containing a single AGG codon. L-p-Phenylazophenylalanine, L-2-anthrylalanine, L-1-naphthylalanine, L-2-naphthylalanine and L-p-biphenylalanine were successfully incorporated into a polypeptide, but l-1-pyrenylalanine was not. The polypeptides containing the nonnatural amino acids showed photofunctionalities.

Recognition of UUN codons by two leucine tRNA species from Escherichia coli

Codon recognition by Escherichia coli tRNA(Leu)4 and tRNA(Leu)5 was investigated by analysis of the competition between two aminoacyl-tRNA species in an in vitro protein synthesis. Both tRNA species strictly obey the wobble rule when they are in competition with other tRNA species. This is probably due to the post-transcriptional modifications at the first position of the anticodon of these tRNA(Leu) species, supporting the proposal that the conformational rigidity of post-transcriptionally modified pyrimidine nucleotides guarantees the correct codon recognition.

Sodium channel mRNAs in cultured spinal cord astrocytes: in situ hybridization in identified cell types

The expression of rat brain sodium channel alpha-subunit mRNAs I, II and III and a putative glial cell-specific sodium channel (NaG) mRNA was examined in cultured astrocytes from P-0 rat spinal cord by RNA blot hybridization and by non-isotope in situ hybridization cytochemistry utilizing two independent sets of isoform-specific RNA probes. Sodium channel mRNA I was not detectable in the cultured astrocytes by RNA blot or in situ hybridization. Sodium channel mRNA II showed negligible-to-low levels of expression in flat, fibroblast-like and 'pancake' astrocytes at 4 days in vitro (div), while stellate, process-bearing astrocytes exhibited low-to-moderate levels of mRNA II expression. At 7 div, mRNA II expression ranged from low-to-moderate in flat astrocytes and was moderately high in most process-bearing astrocytes. In RNA blots, a weak band was observed at 9.5 kb. Sodium channel mRNA III expression was negligible in flat astrocytes and was detectable in low-to moderate levels in stellate astrocytes beginning at 4 div; by 7 div, mRNA III was detectable in low levels in flat astrocytes and low-to-moderate levels in stellate astrocytes. RNA blots showed two bands of nearly equal intensity, one at 9.0 kb and one at 7.2 kb. NaG mRNA showed increased expression with time in culture, being detectable in flat and stellate astrocytes at 4 div and becoming very prominent in flat astrocytes at extended times in culture. In RNA blots of cultured astrocytes at 7 div, a strong hybridizing signal with the NaG probe was observed. These observations demonstrate that flat and stellate astrocytes cultured from rat spinal cord express rat brain sodium channel mRNA II and III, and NaG, and suggest that astrocytes in vitro may co-express multiple forms of sodium channel mRNA.

Changes in concentrations of dopamine, serotonin, and their metabolites induced by carbon monoxide (CO) in the rat striatum as determined by in vivo microdialysis

Striatal microdialysis was performed in rats exposed to carbon monoxide (CO). Extracellular changes of dopamine, serotonin, and their metabolites were monitored before and after CO exposure at 15-min intervals by HPLC analysis. After CO exposure, extracellular dopamine increased (3.8 times that of baseline), whereas 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) decreased (by 20-25% of baseline). The decrease in HVA at individual time points, however, was not significant. After a transient increment of the dopamine, it was cleared from the extracellular fluid within 45 min and reached a stable level. Serotonin and 5-hydroxyindoleacetic acid (5-HIAA) showed a pattern different to that of dopamine and its acid metabolites, i.e., the changes in extracellular levels were small. Pretreatment with dizocilpine (MK-801), a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, 45 min before CO exposure antagonized the changes in the extracellular concentration of DOPAC. However, the change in dopamine levels was not antagonized by pretreatment with MK-801. MK-801 itself had no effect on the levels of monoamines. Therefore, NMDA receptors may not have an important role for regulating striatal dopamine neurons in hypoxic condition.

[Use of radiopaque markers for the diagnosis and management of small bowel obstruction]

Radiopaque markers were used for the diagnosis and management of small bowel obstruction (SBO) due to adhesion in 50 patients. Conservative therapy was begun after the patients received a capsule containing 20 radiopaque markers. The movement of the markers in the gastrointestinal tract was evaluated on X-P after 6, 12, 24, and 48 hours. On supine abdominal X-P, the abdomen was divided by a straight line connecting the right costophrenic angle and the left anterior superior iliac spine, thus defining an upper and lower abdominal segment. After 24 hours, the number of markers in the upper abdominal segment was 4.1 +/- 4.5 in 30 patients who recovered within 7 days, and 16.7 +/- 3.8 in 20 patients who required more than 7 days of conservative therapy (mean +/- SD). In cases requiring long-term management with conservative therapy, the markers in the small bowel were calculated on a daily basis using X-P. On day 7, there were more than 10 markers in the small bowel of 7 patients who underwent surgery. By using radiopaque markers, it was possible after 24 hours to differentiate patients with SBO who would need long-term management, and to determine the limits of conservative therapy and the timing for surgery.

Selective transfer of cholesteryl ester over triglyceride by human plasma lipid transfer protein between apolipoprotein-activated lipid microemulsions

The substrate-specific rate of the human plasma lipid transfer protein (LTP) reaction was studied using pyrene-labeled substrate lipid analogues as probes for various lipids, by monitoring the ratio of the fluorescence intensities of their excimers to those of their monomers as an indicator of pyrene concentration in the microenvironment. Transfer of cholesteryl ester (CE) and triglyceride (TG) was demonstrated between human high-density lipoproteins, between low-density lipoproteins, and between these two lipoprotein, and the specific fractional transfer rate of CE was always higher than that of TG by a factor of 2.4-7.9. On the other hand, the transfer by LTP of CE, TG, and phosphatidylcholine (PC) was also demonstrated between lipid microemulsions having an average diameter of 25-26 nm using the same probes, but only when the emulsions were activated by apolipoproteins A-I, A-II, E, or C-III. The maximally activated rates of the transfer of CE and TG were the same when measured between the emulsions with cores composed exclusively of either lipid. The specific fractional transfer rate of pyrene-CE, however, was inversely proportional to the percentage of CE in the TG core of the emulsions, and the initial transfer of TG was almost completely inhibited by the presence of small percentages of CE in the TG core. Thus, the transfer of CE between the emulsions is highly selective over that of TG by orders of magnitude, much more selective than the reaction between any natural plasma lipoproteins, but this selectivity is not a rate-limiting step of the overall LTP reaction. The maximally activated LTP-catalyzed transfer rate of PC between the emulsions was somewhat higher than that of CE or TG and was not affected by the composition of the core lipids of the emulsion, TG or CE. When an excess amount of LTP was incubated with emulsion containing a small percentage of pyrene-CE in the TG core in the absence of the acceptor particles, excimer fluorescence rapidly decreased to the base line, and this change was suppressed when pyrene-CE was diluted with CE in the core. This result may indicate that LTP selectively disrupts pyrene-CE excimer formation on the basis of its selective interaction with the CE molecule over TG in the emulsion system as a putative background mechanism for the selective transfer of CE.

B2 bradykinin receptors in NG108-15 cells: cDNA cloning and functional expression

Two distinct cDNAs encoding bradykinin receptors (BKRs) were cloned from NG108-15 neuroblastoma-glioma hybrid cells. One was identical with rat uterus B2 BKR, whereas the other one (mBKR) had 91% amino acid homology to the rat B2 BKR and 82% homology to human B2 BKR. Southern blot analysis and genomic DNA cloning revealed that mBKR is derived from the mouse genome. The mBKR, expressed in Xenopus oocytes and COS-7 cells, produced functional BKRs that exhibited the properties of smooth muscle type B2 BKR. These results suggest that both the rat and mouse B2 BKRs of the smooth muscle type are expressed in NG108-15 cells.

Immunohistochemical localization of acidic and basic fibroblast growth factors in human benign and malignant thyroid lesions

The localization of acidic fibroblast growth factor (aFGF) and basic fibroblast growth factor (bFGF) was investigated immunohistochemically in human benign and malignant thyroid lesions. Immunostaining for aFGF and bFGF displayed diffuse or granular deposits of the reaction products in the cytoplasm of neoplastic cells, especially in the marginal region of follicular adenoma, follicular carcinoma and papillary carcinoma. All lesions except for diffuse hyperplasia, which was completely negative in immunostaining for all antibodies, showed an increased immunostaining for bFGF (Ab-1) over that of aFGF and bFGF (Ab-2). Basement membranes of follicular and papillary structure and the fibroblasts located in the stromal tissues were free from immunostaining for all antibodies. The ratio of positive immunostaining for all antibodies was highest in papillary carcinoma, with an incidence of more than 80.0%, followed, in descending order, by widely invasive follicular carcinoma, minimally invasive follicular carcinoma, follicular adenoma and normal thyroid, in which some follicular cells exhibited weak reaction products. aFGF with a molecular weight of 18 kDa was identified in papillary carcinoma of the thyroid. From these data, we concluded that aFGF is synthesized in the neoplastic follicular cells of the thyroid, and aFGF and bFGF may have important roles in the neoplastic proliferation of follicular cells.

Massive apoptosis in infantile myofibromatosis. A putative mechanism of tumor regression

Two cases of solitary infantile myofibromatosis (IM) are presented. Solitary IM are tumors prone to spontaneous regression. Histopathologically, several tumor lobules in our IM cases had central areas of massive cell death, with nuclear pyknosis, cytoplasmic hyalinization and nuclear fragmentation but without lymphoid or neutrophilic cell infiltration. These central cell death areas consisted of about 40% in case 2 and 50% in case 1 of the entire tumor tissues, respectively. Electron microscopy revealed that the condensed nuclei and cytoplasm were fragmented into "apoptotic bodies", with or without phagocytosis by histiocytes. DNA fragmentation, as evidenced by the terminal deoxy transferase-mediated uptake of biotinylated dUTP, was identified at massive cell death areas on paraffin sections from both cases. A characteristic 180- to 190-bp nucleosomal ladder was detected in DNA obtained from the tumor cells in case 1. The collective evidence suggested that these tumors underwent a central, massive apoptosis. As massive cell death similar to that seen in the present cases has been described in other documented cases of IM, we propose that the spontaneous regression that frequently occurs with this type of tumor may be mediated by massive apoptotic cell death.

Sodium channel mRNAs I, II and III in the CNS: cell-specific expression

The cellular localization of rat brain sodium channel alpha-subunit mRNAs I, II and III in the central nervous system (CNS) was examined by non-isotope in situ hybridization cytochemistry utilizing two independent sets of isoform-specific RNA probes, one set recognizing sodium channel isoforms in the coding region and the other in the non-coding region of the sodium channel messages. The independent sets of probes demonstrated qualitatively similar patterns of sodium channel mRNA expression. In the hippocampus, sodium channel mRNA I was very weakly expressed in the pyramidal layer and in the granular layer of the dentate gyrus; in contrast, sodium channel mRNA II was strongly expressed by neurons in these regions. Sodium channel mRNA III exhibited low-to-moderate expression in some neurons of the pyramidal layer of the hippocampus and granular layer of the dentate gyrus, and was not detectable in others. In the cerebellum, sodium channel mRNA I was moderately expressed in some Purkinje cells, weakly expressed in scattered cells in the molecular layer and negligibly expressed in the granular layer. Sodium channel mRNA II was strongly expressed in Purkinje and granule cells, and was moderately expressed in some cells in the molecular layer. Sodium channel mRNA III was generally not detectable in the cerebellum. In the spinal cord, motor neurons and scattered neurons throughout the gray matter exhibited moderate-to-strong expression of both sodium channel mRNA I and II. A population of cells in the spinal zone of Lissauer showed heavy expression of mRNA II, but not mRNA I. Sodium channel mRNA III was not detectable in spinal cord neurons. These observations are consistent with a general regional distribution of sodium channel message isoforms, with mRNA II being preferentially expressed in rostral regions of the CNS and mRNA I in caudal regions. However, the results also indicate that different cell types, within a given region, display different patterns of sodium channel mRNA expression. Moreover, these data suggest that individual neurons may express multiple forms of sodium channel mRNA.

[Detection of mycobacterial DNA by in vitro enzymatic amplification in lung nodular lesions in a patient with ovarian immature teratoma]

We experienced a 13-year-old girl with ovarian immature teratoma, who presented multiple pulmonary nodular lesions. Thoracotomy was performed to rule out the metastatic tumor. Histopathological study of the resected tumor suggested a possible diagnosis of tuberculosis. However, neither the acid-fast staining nor the mycobacterial culture of the specimens confirmed the diagnosis. Polymerase chain reaction (PCR) and hybridization technique successfully detected specific DNA sequence for M. tuberculosis from the specimens. The lesions regressed after anti-mycobacterial therapy. Detecting mycobacterial DNA by PCR, which led to a proper diagnosis and treatment of this patient, is a rapid and sensitive method in diagnosis of tuberculosis. This method is recommended to distinguish tuberculosis from neoplastic lesions of the lung, where surgical intervention is necessary.

Molecular recognition of the identity-determinant set of isoleucine transfer RNA from Escherichia coli

Molecular recognition of Escherichia coli tRNA(Ile) by the cognate isoleucyl-tRNA synthetase (IleRS) was studied by analyses of chemical footprinting with N-nitroso-N-ethylurea and aminoacylation kinetics of variant tRNA(Ile) transcripts prepared with bacteriophage T7 RNA polymerase. IleRS binds to the acceptor, dihydrouridine (D), and anticodon stems as well as to the anticodon loop. The "complete set" of determinants for the tRNA(Ile) identity consists of most of the nucleotides in the anticodon loop (G34, A35, U36, t6A37 and A38), the discriminator nucleotide (A73), and the base-pairs in the middle of the anticodon, D and acceptor stems (C29.G41, U12.A23 and C4.G69, respectively). As for the tertiary base-pairs, two are indispensable for the isoleucylation activity, whereas the others are dispensable. Correspondingly, some of the phosphate groups of these dispensable tertiary base-pair residues were shown to be exposed to N-nitroso-N-ethylurea when tRNA(Ile) was bound with IleRS. Furthermore, deletion of the T psi C-arm only slightly impaired the tRNA(Ile) activity. Thus, it is proposed that the recognition by IleRS of all the widely distributed identity determinants is coupled with a global conformational change that involves the loosening of a particular set of tertiary base-pairs of tRNA(Ile).

Value of thallium-201 early reinjection for assessment of myocardial viability

To assess the efficacy of early reinjection for predicting post intervention improvement in thallium-201 (T1) uptake and regional wall motion, we reinjected a small dose of T1 following post-stress imaging and obtained reinjection early images (10 min after early reinjection) and reinjection delayed images (3 hr afterwards) in 40 patients who were referred to us for revascularization (group I). Twenty-nine patients in group I also underwent conventional stress-redistribution T1 scintigraphy (group II). Conventional stress-redistribution T1 scintigraphy was repeated after intervention. Contrast left ventriculography was performed before and after intervention and changes in regional wall motion were assessed in 22 of 40 patients. In group I, the predictive value for improvement and no improvement (the accuracy) of reinjection early images in perfusion was 83%, while that of reinjection delayed images was 91%. Furthermore, the accuracy of reinjection early images in regional wall motion was 80%, while it was 91% for reinjection delayed images. In group II, the accuracy in perfusion was 78% and the value in regional wall motion was 70%. Both accuracy in perfusion and in regional wall motion obtained from reinjection delayed images were significantly higher than the values in group II (p < 0.05). These data suggest that early reinjection is useful for predicting postintervention thallium uptake and regional wall motion.

Disparity between sensory nerve activity and psychophysical responses for air-puff stimulation of the index finger and palm in man

Air-puff stimuli were delivered to five successive sites over the index finger and palm to obtain psychophysical responses and to record sensory nerve action potentials (SNAPs) from the median nerve at the wrist for elucidating psychoneural correlations across different locations of the glabrous hand. Magnitude estimations at each location evoked uniform subjective magnitudes for all stimulus locations. The time-integral of all SNAP components was the largest at the finger tip and the smallest at the most proximal site over the palm in agreement with the reported receptor density gradient across the finger and palm. Thus, the constant magnitude estimations with different quantities of peripheral afferent inputs across areas imply that the central nervous system plays a major role in shaping subjective magnitude estimation across different locations.

Intermode beat stabilized laser with frequency pulling

A frequency-stabilized two-mode He-Ne laser has been developed. The intermode beat frequency of the experimental laser was approximately 600 MHz for a 25-cm cavity. The laser frequency in which the mode stands is pulled to the center of the gain curve (frequency pulling). The degree of pulling depends on where the longitudinal modes stand in the broadened gain curve. Beat frequency is thereby changed periodically of the order of hundreds of kilohertz with respect to cavity expansion. The frequency pulling was effectively used for frequency stabilization of the laser. The standing position of the longitudinal mode lights was locked in the gain curve by controlling the change of intermode beat frequency. A microwave mixer was applied to extract the frequency change of the intermode beat. Excellent frequency stability (10(10) for the laser oscillation and 10(6) for the beat frequency) was attained. The polarization orthogonality of the proposed laser was superior to that of Zeeman lasers.

Site-directed mutagenesis, fluorescence, and two-dimensional NMR studies on microenvironments of effector region aromatic residues of human c-Ha-Ras protein

The Tyr residues in positions 32 and 40 of human c-Ha-Ras protein were replaced by site-directed mutagenesis (Y32F, Y32W, Y40K, and Y40W) to examine their roles in the signal-transducing activity and the sensitivity to the GTPase activating protein (GAP). The signal-transducing activity of the oncogenic Ras protein in PC12 cells was lost upon mutations Y32F and Y40K, but retained upon mutations Y32W and Y40W. These results suggest that residues 32 and 40 are both required to have aromatic groups and residue 32 is further required to have a hydrogen donor. On the other hand, three mutations (Y32F, Y32W, and Y40W) caused no appreciable reduction in either GAP-binding affinity or GAP sensitivity. By the Y40K mutation, GAP-binding affinity was slightly lowered, while GAP sensitivity was drastically impaired. Therefore, for residues 32 and 40 of Ras, interactions with GAP appear to be different from those with the target of signal transduction in the PC12 cell. As for the Y32W-Ras protein bound with an unhydrolyzable GTP analogue (GMPPNP), the Trp32 fluorescence is appreciably red-shifted, weaker, and more susceptible to KI quenching as compared to that of the GDP-bound form. Two-dimensional NMR spectroscopy with selectively deuterated Ras proteins revealed fewer and weaker nuclear Overhauser effects on the aromatic protons of Trp32 in the GMPPNP-bound form than in the GDP-bound form. This indicates that the side chain of Trp32 is more exposed to the solvent in the GMPPNP-bound form than in the GDP-bound form.(ABSTRACT TRUNCATED AT 250 WORDS)

Gene duplications and evolution of the short wavelength-sensitive visual pigments in vertebrates

When invertebrate rhodopsins were used as the outgroup, the rooted phylogenetic tree of 26 vertebrate visual pigments (VPs) was constructed. These VPs are distinguished into the following four clusters: (1) RH1 cluster consisting of rhodopsins, (2) RH2 cluster consisting of VPs with variable ranges of absorption spectra, (3) SWS cluster of short wavelength-sensitive VPs, and (4) LWS/MSW cluster of long and medium wavelength-sensitive VPs. Short wavelength-sensitive VPs from Astyanax fasciatus (AF23), goldfish (BCa), chicken (BCg and VGg), and human (BHs) belong to SWS cluster, whereas that from gecko (BGge) belongs to the RH2 cluster. The SWS cluster is further divided into SWS-I (BHs and VGg) and SWS-II (AF23, BCa, and BGg) groups. The SWS-I group has accumulated more amino acid changes than any other group of VPs. It is suggested that amino acid changes at a few key positions might have been important in the functional differentiation of the SWS-I group from the SWS-II group.