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Oxidation of ribosomal protein L12 with hydrogen peroxide converts the three methionine residues to methionine sulfoxide. The oxidized protein has a decreased ability to bind to ribosomes, interact with ribosomal protein L10, be precipitated by L12 antiserum, and serve as substrate for the acetylating enzyme that converts L12 to L7. Full activity of L12 is regaine when the protein is reduced with 2-mercaptoethanol. Sedimentation equilibrium analysis shows that oxidation of the methionine residues in L12 causes the conversion of the protein from the dimer to the monomer form, and the results indicate that the dimer is the active form of the protein in the above reactions.The ease with which Escherichia coli ribosomal protein L12, and its acetylated derivative L7, can be specificially removed from the ribosome (1) has permitted detailed studies on their role in protein synthesis. The 50S ribosomal subunit lacking L7/L12 cannot interact properly with the soluble factors involved in the initiation (2-5), elongation (1,6,7), and termination (8) steps of protein synthesis, and, therefore, the hydrolysis of GTP that is associated with these partial reactions does not occur with L7/L12-depleted ribosomes (1-7). The activity of L7/L12-depleted 50S subunits can be restored by the addition of L7/L12 because these proteins rapidly bind to the large subunit (9). It is of interest that there are four equivalents of L7/L12 per ribosome, whereas the other E. coli ribosomal proteins are present in one copy per ribosome (10,11). Although the ratio of L7 to L12 on the ribosome varies under different growth conditions (12), no function of L12 has been observed that cannot be performed by L7, and vice versa (3, 8, 9, 13).There also is considerable information available on the chemical nature of the L7 and L12 proteins. They have molecular weights of 12,200, and the amino acid sequences are known (14,15). Serine is the NH2-terminal amino acid, and the difference between the two is that L7 has an acetylated NH2-terminus. The enzyme that catalyzes the acetylation has been purified, and it has been shown that free L12 is acetylated 10 times faster than ribosomal-bound L12 (16). It is also of interest that these proteins lack cysteine, histidine, tryptophan, and tyrosine, are very acidic (pI = 4.7-4.9), and have a high degree of secondary structure with >45% helical content (17)(18)(19). The proteins in solution form dimers (14,20,21) that may be the functional form on the ribosome and also bind tightly to ribosomal protein L10 (22,23). Other results suggest that L10 on the ribosome is also required for L7/L12 to bind to the ribosome (24,25). In this regard an NH2-terminal fragment of L12, containing 73 amino acids, can bind to L7/ L12-depleted ribosomes but does not restore their biological activity (26).Because little is known about the structure-function rela- 2 Mug of EF-G, and control or treated L12 as indicated. The mixtures were preincubated for 60 sec at 370C and then the reaction was started by the addition of 8 pmol of...

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This article presents data from a large-scale cross-sectional survey of LGBTQ college students ( N = 1,123) reflecting on their middle and high school experiences in choral music. The quantitative data indicate that students felt safer in high school than in middle school and that a small majority of high school teachers voiced support for LGBTQ students. These data indicate that high school choral classrooms were perceived as safe for a majority of respondents. The open-ended responses highlight themes including: the plight of transgender students who faced difficulty navigating their gender identities in the choral environment, the importance of enumerated non-discrimination policies, and the importance of words/semantics. Respondents discussed helpful and hurtful words and/or policies that influenced their choral experiences. A main theme was encouragement of open acknowledgement of LGBTQ identities and issues in the choral classroom. Suggestions for teaching practice and policy are provided based upon these data.

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