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The active site of human immunodeficiency virus reverse transcriptase (HIV1-RT) was probed using three group-specific reagents: phenylglyoxal (PG), N-ethylmaleimide (NEM), and pyridoxal 5'-phosphate (PLP). The inactivation of HIV1-RT by arginine-specific PG was found to be completely protected against by adding primer-template. The potential active site arginine was localized to position 277 in the primary structure, suggesting that the polymerase domain of the enzyme should be considered as extending at least this far from the N terminus. The sulfhydryl-modifying reagent NEM completely inhibits NY5-HIV1-RT, which contains a cysteine at position 162, and such inhibition is protected against by primer-template. However, it does not strongly inhibit LAV-HIV1-RT, in which C162 is replaced by S162, indicating that while C162 may be at or near the active site or interact allosterically with primer-template, it is not essential for activity. The lysine-specific reagent PLP was found to be a noncompetitive inhibitor with respect to both primer-template [poly(rA).oligo(dT)] and dTTP. The latter result differentiates HIV1-RT from other RTs, for which PLP has been shown to be a competitive inhibitor with respect to dTTP.

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Despite the tremendous growth in theory and research on emerging adulthood over the past decade, relatively little attention has been paid to the experiences of emerging adults from ethnic minority backgrounds. The purpose of this chapter is to fill this gap by conducting a conceptual review of the literature on race, ethnicity, and emerging adulthood. The authors begin with a discussion of conceptual issues, clarifying terms such as emerging adults, emerging adulthood, race, and ethnicity. The existing literature is reviewed pertaining to the five pillars of emerging adulthood: the age of instability, possibilities, self-focus, in-betweenness, and identity explorations. The chapter closes with a discussion of major challenges to conducting research on race, ethnicity, and emerging adulthood. Taken together, this review is intended to provide a broad overview of the state of knowledge and inspire future research.