Essays on Economics of Entrepreneurship

This dissertation examines three important issues. The first issue is about the human capital investment and entrepreneurship as a career choice. The standard human capital theory shows that firms (employees) never invest in general (firm-specific) human capital of the employee as they do not extract any return from it. However, when entrepreneurship is introduced as a career option for an innovative employee, both firm’s and employee’s human capital investments change. Employee starts investing in his firm-specific human capital to increase the probability to innovate (and to become an entrepreneur). However, the firm uses general human capital investment to reduce the risk of employee’s departure. The second issue is regarding the factors motivating entry regulations reforms and the possible nonlinear effects of entry regulation reforms. The current literature and the policy recommendations assume that these reforms have linear effects on entrepreneurship. Nevertheless, the anecdotal evidence shows that the outcomes of such reforms vary greatly from country to country. To investigate this issue, I collect a sample data on entry regulations and firm creation from World Bank. The empirical analysis indicates that the effect of entry regulation reforms depends on the pre-reform level of bureaucracy in the country. More specifically, while low-bureaucracy countries benefit from entry regulation reforms, high-bureaucracy countries do not benefit. Moreover, the probability of making a reform increases if the country has reformist neighbors, cumbersome entry regulations, high unemployment rate, or low corruption level. The last issue is related to the individual and joint effects of bureaucracy and corruption on different types of entrepreneurs. The current literature investigates these effects only on unified measures of entrepreneurship. However, entrepreneurs are very different in many senses. To address this issue, I collect the necessity-based and opportunity-based entrepreneurship data from Global Entrepreneurship Monitor. The empirical analysis yield two important results: First, bureaucracy has a direct negative (positive) effect on necessity-based (opportunity-based) entrepreneurs. Second, corruption mitigates the effect of bureaucracy for both groups of entrepreneurs. All three chapters offer useful insights and important implications to academics and policymakers.

Functional characterization of a Kar3/Vik1-like Kinesin-14 heterodimer from the filamentous multinucleate fungus Ashbya gossypii

Kinesins are motor proteins that convert chemical energy from ATP hydrolysis into mechanical energy used to generate force along microtubules, transporting organelles, vesicles, and proteins within the cell. Kar3 kinesins are microtubule minus-end-directed motors with pleiotropic functions in mating and mitosis of budding and fission yeast. In Saccharomyces cerevisiae, Kar3 is multifunctionalized by two non-catalytic companion proteins, Vik1 and Cik1. A Kar3-like kinesin and a single Vik1/Cik1 ortholog are also expressed by the filamentous fungus Ashbya gossypii, which exhibits different nuclear movement challenges and unique microtubule dynamics from its yeast relatives. We hypothesized that these differences in A. gossypii physiology could translate into interesting and novel differences in its versions of Kar3 and Vik1/Cik1. Presented here is a structural and functional analysis of recombinantly expressed and purified forms of these motor proteins. Compared to the previously published S. cerevisiae Kar3 motor domain structure (ScKar3MD), AgKar3MD displays differences in the conformation of the ATPase pocket. Perhaps it is not surprising then that we observed the maximal microtubule-stimulated ATPase rate (kcat) of AgKar3MD to be approximately 3-fold slower than ScKar3MD, and that the affinity of AgKar3MD for microtubules (Kd,MT) was lower than ScKar3MD. This may suggest that elements that compose the ATPase pocket and that participate in conformational changes required for efficient ATP hydrolysis or products release work differently for AgKar3 and ScKar3. There are also subtle structural differences in the disposition of the secondary structural elements in the small lobe (B1a, B1b, and B1c) at the edge of the motor domain of AgKar3 that may reflect the enhanced microtubule-depolymerization activity that we observed for this motor, or they could relate to its interactions with a different regulatory companion protein than its budding yeast counterpart. Although we were unable to gain experimentally determined high-resolution information of AgVik1, the results of Phyre2-based bioinformatics analyses may provide a structural explanation for the limited microtubule-binding activity we observed. These and other fundamental differences in AgKar3/Vik1 could explain divergent functionalities from the ScKar3/Vik1 and ScKar3/Cik1 motor assemblies.