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We test the empirical validity of the Capital Asset Pricing Model (CAPM) on the Zimbabwe Stock Exchange (ZSE) using cross-sectional stock returns on 31 stocks listed on the ZSE between March 2009 and February 2014. We conclude that, although the explanatory power of beta tends to fall rapidly for prediction horizons greater than 6 months, beta significantly explains average monthly stock returns on the ZSE. Tests to validate the CAPM reject its validity for the ZSE however, primarily due to liquidity and skewness anomalies. We nevertheless fail to detect any size effects. There is encouraging evidence to suggest that the CAPM performs reasonably well in predicting average monthly returns over prediction horizons of between 3 and 6 months. We recommend that investors and analysts must exercise extreme caution in applying the CAPM. Furthermore, we discourage strategies based on the existence of a size premium on the ZSE. Instead, investors may consider neglected and negatively skewed stocks, albeit over appropriate horizons. Further research on other African stock markets will help verify if the optimal performance range of the CAPM is indeed 3 to 6 months. Development of standard continental proxy market portfolios will also improve the estimation of betas and enhance results of cross-country tests of the CAPM.

The study employs the Granger causality test in a multivariate cointegration and error correction environment to examine the relationship between financial development and economic growth in Zimbabwe. Using annual data from 1980 to 2012, and after controlling for financial and monetary reforms, the study demonstrates a unidirectional causal relationship that runs from financial development to economic growth. The evidence shows that financial development; banking sector development in particular, is not a passive response to economic growth. Instead, it is a critical tool for accelerating economic growth. Policy implications of this evidence are that the banking sector in Zimbabwe must be supported with policies that encourage credit expansion and innovation to support economic growth. The equities market, on the other hand, requires more investor-friendly innovations and policies, especially with regard to trading efficiency and foreign investor participation in the primary market. In combination, these policy interventions should be able to magnify the positive effect of financial development on economic growth.

The concepts of protein purification are often taught in undergraduate biology and biochemistry lectures and reinforced during laboratory exercises; however, very few reported activities allow students to directly gain experience using modern protein purification instruments, such as Fast Protein Liquid Chromatography (FPLC). This laboratory exercise uses size exclusion chromatography (SEC) and ion exchange (IEX) chromatography to separate a mixture of four different proteins. Students use an SEC chromatogram and corresponding SDS-PAGE gel to understand how protein conformations change under different conditions (i.e. native and non-native). Students explore strategies to separate co-eluting proteins by IEX chromatography. Using either cation or anion exchange, one protein is bound to the column while the other is collected in the flow-through. In this exercise, undergraduate students gain hands-on experience with experimental design, buffer and sample preparation, and implementation of instrumentation that is commonly used by experienced researchers while learning and applying the fundamental concepts of protein structure, protein purification, and SDS-PAGE. © 2016 by The International Union of Biochemistry and Molecular Biology, 45(1):60-68, 2017., (© 2016 The International Union of Biochemistry and Molecular Biology.)

NOXO1β [NOXO1 (Nox organizer 1) β] is a cytosolic protein that, in conjunction with NOXA1 (Nox activator 1), regulates generation of reactive oxygen species by the NADPH oxidase 1 (Nox1) enzyme complex. NOXO1β is targeted to membranes through an N-terminal PX (phox homology) domain. We have used NMR spectroscopy to solve the structure of the NOXO1β PX domain and surface plasmon resonance (SPR) to assess phospholipid specificity. The solution structure of the NOXO1β PX domain shows greatest similarity to that of the phosphatidylinositol 3-kinase-C2α PX domain with regard to the positions and types of residues that are predicted to interact with phosphatidylinositol phosphate (PtdInsP) head groups. SPR experiments identify PtdIns(4,5)P(2) and PtdIns(3,4,5)P(3) as preferred targets of NOXO1β PX. These findings contrast with previous lipid overlay experiments showing strongest binding to monophosphorylated PtdInsP and phosphatidylserine. Our data suggest that localized membrane accumulation of PtdIns(4,5)P(2) or PtdIns(3,4,5)P(2) may serve to recruit NOXO1β and activate Nox1., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Apoptosis inducing factor (AIF) is a mediator of caspase-independent cell death that is also necessary for mitochondrial energy production. How these seemingly opposite cellular functions of AIF are controlled is poorly understood. X-linked inhibitor of apoptosis (XIAP) is an endogenous inhibitor of caspases that also regulates several caspase-independent signaling pathways. The RING domain of XIAP possesses E3 ubiquitin ligase activity, though the importance of this function to signal regulation remains incompletely defined. XIAP binds and ubiquitinates AIF, and in this study, we determined the functional consequences of XIAP-mediated AIF ubiquitination. Unlike canonical ubiquitination, XIAP-dependent AIF ubiquitination did not lead to proteasomal degradation of AIF. Experiments using ubiquitin mutants demonstrated that the XIAP-dependent ubiquitin linkage was not formed through the commonly used lysine 48, suggesting a noncanonical ubiquitin linkage is employed. Further studies demonstrated that only lysine 255 of AIF was a target of XIAP-dependent ubiquitination. Using recombinant AIF, we determined that mutating lysine 255 of AIF interferes with the ability of AIF not only to bind DNA but also to degrade chromatin in vitro. These data indicate that XIAP regulates the death-inducing activity of AIF through nondegradative ubiquitination, further defining the role of XIAP in controlling AIF and caspase-independent cell death pathways.

NOXO1 (Nox Organizer 1) is a homolog of the NAPDH oxidase protein p47(phox). NADPH oxidases transfer electrons from NADPH to molecular oxygen, generating the superoxide anion. NOXO1 contains an N-terminal PX (phox homology) domain and is one of several PX domain-containing proteins found in the cytosolic subunits of the NADPH oxidase complex. These PX domains bind to membrane lipids and target the protein to membranes, recruiting other cytosolic components to the membrane bound components and aiding formation of a active enzyme complex. This recruitment represents a level of regulation of these oxidases. Here we report the backbone assignments of NOXO1β PX.